LONDON - Britain's parliament voted heavily in favor of legalizing gay marriage on Tuesday, but Prime Minister David Cameron's authority in his own party took a blow as his Conservatives split in two over the measure he had championed.

In the first of several votes required for its passage, the lower house of parliament backed the legislation by 400-175, but more than half of Cameron's 303 lawmakers voted against or abstained, signaling deep unease with it and his leadership.

During a debate that lasted more than six hours, many Conservative MPs denounced the legislation, saying it was morally wrong, not a public priority, and unnecessarily divisive, threatening a corrosive legacy of bitterness.

Conservative lawmaker Gerald Howarth told parliament that the government had no mandate to push through a "massive social and cultural change."

"This is not evolution, it's revolution," added Edward Leigh, another Conservative member of parliament, saying marriage was "by its nature a heterosexual union."

Although the vote went Cameron's way, many analysts believe he will now have to address a deep seam of discontent running through his party.

He made a last minute televised statement ahead of the vote, arguing gay marriage would make society stronger.

"I'm a big believer in marriage. It helps people to commit to each other, and I think that's why gay people should be able to get married too," he said.

He later hailed the result of the vote as "a step forward for our country."

Cameron is trying to perform a tricky balancing act: to reconcile his desire to show his party is progressive, with the views of many in it who are uncomfortable with such a reform.

Amid talk of a possible leadership challenge to Cameron, many Conservative lawmakers say the prime minister is sacrificing core party values on the altar of populism.

---

"He hasn't got a lot of political capital left in the bank," Stewart Jackson, a Conservative MP who opposes the gay marriage bill, told Reuters before the vote. "He has to deliver some authentic Conservative policies very soon."

Such talk is rife among some Conservative lawmakers and follows a spate of articles in the British press in which a handful of MPs raised the possibility of ousting Cameron, a prospect most commentators regard as far-fetched before the next election in 2015.

Grievances against Cameron
Conservative MPs' grievances are many: that Cameron is "arrogant," that he is too fond of the European Union, that the party's policies have been diluted by its coalition partner after Cameron failed to win the last election outright, and a nagging fear that he will not win the next one.

The gay marriage initiative has infuriated rank-and-file party activists and a protest letter signed by 25 past and present chairmen of local Conservative associations warned that members were starting to resign over the issue.

Justin Welby, the newly elected Archbishop of Canterbury and head of the world's 80 million Anglicans, used his first comments after being confirmed on Monday to reiterate his own opposition to gay marriage.

Faced with strong opposition from the Anglican and Catholic churches, the law would not force them to conduct gay marriages, but critics say gay people may launch legal challenges.

A YouGov poll for the Sunday Times on Sunday showed 55 percent favored legalizing gay marriage, while 36 percent opposed it. However, the same poll showed the issue was not one that concerned most voters.

The new law proposes legalizing same-sex marriage in 2014. It would also allow civil partners to convert their partnerships into marriages.

Gay marriage supporters say that while existing civil partnerships for same-sex couples afford the same legal rights as marriage, the distinction implies they are inferior.

In a sometimes emotional debate on Tuesday, several gay MPs from different parties took to their feet to commend the bill, describing the prejudice they had suffered growing up.

"Millions will be watching us today," said Nick Herbert, a gay Conservative MP. "Not just gay people but people who want to live in an equal society."

The vote was warmly welcomed by Cameron's junior coalition partners, the Liberal Democrats, and by the opposition Labour party, while gay rights group Stonewall called the result "a truly historic step forward."

Tuesday's vote in the House of Commons was "free," meaning MPs were able to vote according to their conscience, rather than under party orders.

The bill is still many stages away from becoming law, and some of its opponents called on Cameron after the vote to consider amending it to appease their concerns, promising they would try to frustrate its progress through parliament.

Warning of divisions
Peter Kellner, president of pollster YouGov, said he felt the parliamentary rebellion would hurt the Conservative party.

"For Cameron, gay marriage is part of his attempt to persuade the voters that his party belongs to modern, 21st century Britain," he wrote on the pollster's site.

"But the divisions that the gay marriages bill has unleashed ... threaten to send an altogether different message: that the Tories are divided, out of touch and prone to quarrel over issues of little concern to most voters."

With the next election still two-and-a-half years distant, there is a risk that internal party splits over issues like gay marriage could fester and turn what for now is only talk of a possible leadership challenge into the real thing.

"David Cameron has split the Conservative Party in half on gay marriage and failed to win a majority of Tory MPs. Labour win," Jackson, the Conservative MP, wrote after the vote.

Copyright 2013 Thomson Reuters. Click for restrictions.

Tens of thousands of people marched through Paris on Sunday to support the French government's plan to legalize gay marriage and adoption, but the turnout fell well short of a mass demonstration against the project two weeks ago.

Police estimated total attendance at about 125,000, while organizers put the number at 400,000. Two weeks ago, organizers of the anti-gay marriage protest claimed turnout of one million, while police put the number at 340,000, an unusually high turnout even in protest-prone France. 

"There is a big difference between today's march and the one two weeks ago, which is that this demonstration is one of brotherhood, not of hatred," Paris mayor Bertrand Delanoe, who is openly gay, said on French television. 

---

"The majority of French people wants all couples to have equality in love and parenthood," Delanoe added. 

On Tuesday, French parliament starts a two-week debate about the planned law change, which would be one of the biggest social reforms since abolition of the death penalty in 1981. 

The government's socialist and green majority is determined to pass the legislation, against which the conservative opposition has lodged some 5,000 amendments. 

On Saturday, an Ifop poll showed the proportion of French supporting legalization of same-sex marriage has risen to 63 percent from 60 percent in early January and December, despite weeks of protest against the planned reform. 

Support for adoption rights for gay couples also rose by 3 percentage points, although the country remains divided on the issue, with 49 percent in favor, according to the firm. 

Several government ministers took part in the march and will be among a string of celebrities at a party organized by Pierre Berge, partner of late fashion designer Yves Saint Laurent. 

Former French Health Minister Roselyne Bachelot was one of the few conservative politicians to support the marchers. 

"Nobody has anything to fear from this step forward," she told BFM television. 

Henri Guaino, a former top adviser to President Nicolas Sarkozy, told BFM the proposed law was a "a denial of nature" and called for a referendum on the issue. 

"It is a negation of the difference between the sexes," he said. 

Opponents of gay marriage and adoption, including most faith leaders in France, have argued that the reform would create psychological and social problems for children. 

Same-sex weddings are legal in 11 countries including Belgium, Portugal, the Netherlands, Spain, Sweden, Norway and South Africa, as well as nine U.S. states and Washington D.C. 

Copyright 2013 Thomson Reuters. Click for restrictions.

PARIS - Several hundred thousand people converged at the Eiffel Tower in Paris Sunday to protest President Francois Hollande's bill to legalize same-sex marriage by June.

Protesters waved pink and blue flags showing a father, mother and two children. Many had taken long train and bus rides from outside Paris.

Hollande has pledged to push through a same-sex marriage law with his Socialist party’s parliamentary majority, but his opponents have dented public support and forced deputies to put off a plan to allow lesbian couples access to artificial insemination.

---

Same-sex marriage is recognized in 11 countries including Belgium, Portugal, the Netherlands, Spain, Sweden, Norway and South Africa. In the U.S., it is legal in nine states and in Washington, D.C.

Champ de Mars, the long park between the Eiffel Tower and the Ecole Militaire, was packed Sunday, with organizers claiming 800,000 protesters, but police more conservatively estimating 340,000 – a large turnout even in France, where protests are a way of life.

"Nobody expected this two or three months ago," said Frigide Barjot, a flamboyant comedian leading the demonstration. At the rally, she read aloud a letter to Hollande asking him to withdraw the bill and hold a public debate on the issue.

Strongly supported by the Catholic Church, opponents of same-sex marriage have mobilized practicing Catholics, members of the extreme far-right Front National party, some Muslims, evangelicals and even a few openly gay people.

They argue that same-sex marriage would cause psychological and social harm to children, which they believe should trump the desire for equal rights for gay adults.

Organizers insist they do not oppose gays and lesbians but rather support what they say are the rights of children to have a father and a mother. Slogans on the posters and banners read, "Marriagophile, not homophobe," "All born of a father and mother" and "Paternity, maternity, equality."

"The French are tolerant, but they are deeply attached to the family and the defense of children," said Daniel Liechti, vice-president of the National Council of French Evangelicals, which urged its members to join the march.

Their efforts appear to have had an impact. Surveys indicate that popular support for gay marriage in France has slipped about 10 points to less than 55 percent since opponents started speaking out. Fewer than half of those polled recently favored giving gay couples adoption rights.

Under this pressure, French legislators dropped a plan that would allow lesbian couples access to artificial insemination.

Hollande's office, recognizing the “substantial” turnout Sunday, said it will not be swayed and that it will continue to push for a law recognizing same-sex marriage. 

More world stories from NBC News:

• 150 years old and still running late: London Tube reaches landmark
• Family escapes 'tornadoes of fire' by clinging to jetty for 3 hours
• Video: How happy is the only country to track happiness?

Follow World News from NBCNews.com on Twitter and Facebook

 

Copyright 2013 Thomson Reuters. Click for restrictions.

PARIS - Several hundred thousand people are expected to march through Paris on Sunday against the planned legalization of same-sex marriage in the first mass protest against the unpopular President Francois Hollande.

Strongly backed by the Catholic hierarchy, lay activists have mobilized a hybrid coalition of church-going families, political conservatives, Muslims, evangelicals and even homosexuals opposed to gay marriage for the show of force.

So many are expected to converge on Paris from around France that police had organizers split it into three separate columns starting from different points around the city and meeting in the Champ de Mars park at the Eiffel Tower.

Virginie Merle, an eccentric comedian known as Frigide Barjot, who is leading the so-called "Demo for All," insists the protest is pro-marriage rather than anti-gay and has banned all but its approved banners saying a child needs a father and a mother to develop properly.

"We're all born of a man and a woman, but the law will say the opposite tomorrow," she said last week. "It will say a child is born of a man and a man."

---

Hollande, who promised to legalize gay marriage and adoption during his election campaign last spring, has a comfortable parliamentary majority to pass the law by June as planned.

But his clumsy handling of other promises, such as a 75 percent tax on the rich that was ruled unconstitutional or his faltering struggle against rising unemployment, has soured the public mood. A mass street protest can hardly help his image.

Marriage or jobs for all?
Same-sex nuptials are already legal in 11 countries including Belgium, Portugal, Netherlands, Spain, Sweden, Norway and South Africa, as well as nine U.S. states and Washington D.C.

Gay marriage opponents such as Cardinal Andre Vingt-Trois, head of the Catholic Church in France, have asked why Hollande is pushing through a divisive social reform called "marriage for all" when voters seem more concerned about "jobs for all."

Vingt-Trois spearheaded the opposition with a critical sermon in August. Other faith leaders -- Muslim, Jewish, Protestant and Orthodox Christian -- soon spoke out too.

Avoiding religious arguments that could put off the secular French, they struck a chord with voters by stressing problems they saw emerging from same-sex marriage rather than letting the government shape the debate as an issue of equal rights only.

Opinion polls show reform zeal cooled somewhat once these arguments were heard. Support for gay nuptials has slipped about 10 points to under 55 percent and fewer than half the French now want gays to have adoption rights.

Under this pressure, legislators dropped a plan to amend the draft law to allow lesbians access to assisted reproduction techniques such as artificial insemination that are now limited to heterosexual couples with fertility problems.

Rival march
Organizers insist they are not against gays and lesbians, but for traditional marriage. "We are marriagophile, not homophobe," said Barjot, author of a book entitled "Confessions of a Trendy Catholic."

Most national faith leaders will not join the protest, but at least eight Catholic bishops have said they would march.

"I'm happy many Catholics will be mobilized, but this is not a church demonstration against the government," said Vingt-Trois, who plans to go meet marchers but not join them.

Opposition leader Jean-Francois Cope and other conservatives, as well as leaders from the far-right National Front, will march as private citizens without political banners.

Civitas, a far-right Catholic group whose protests have been openly anti-gay, plans a rival march that will run parallel to one of the "Demo for All" columns. Organizers say they will have about 10,000 volunteer marshals to keep order during the march.

Copyright 2013 Thomson Reuters. Click for restrictions.

PARIS — French Muslims have begun joining a mostly Catholic-led movement against same-sex marriage, widening opposition to the reform that the Socialist-led government is set to write into the law by June.

Fifty Muslim activists issued an open letter on Monday urging fellow Muslims to join a major Paris protest against the law on Sunday. That followed a similar appeal last Saturday by the influential Union of French Islamic Organizations, or UOIF.

---

Leaders of almost all main faiths in France have spoken out against the law but not called on their followers to march in Sunday's demonstration to avoid giving the opposition campaign an overly religious tone.

Gay-marriage opponents take to streets in France

President Francois Hollande and his government clashed with the Catholic Church last weekend, telling Catholic schools not to discuss the law with their pupils and urging state education officials to report anti-gay discussions at Catholic schools.

"We will protest on January 13 by joining a pluralist campaign to preserve the traditional framework of marriage," the Muslim activists' letter said. "We invite all French Muslims to turn out in large numbers."

The UOIF statement also urged Muslims to join the "March for All", the Paris protest against the reform the government has dubbed "Marriage for All".

"This bill, if it passes, will disrupt family and social structures and civil law dangerously and irreparably," it said.

The Muslim activist letter was signed by intellectuals, business leaders and leaders of several grassroots Muslim groups. It accused the government of using the marriage issue "to mask its ineffectiveness in the fight against unemployment".

More stories from Europe

France's 5-million-strong Muslim minority is Europe's biggest and Islam is the second largest faith after Catholicism.

The government has a comfortable majority in parliament to pass the bill. Opinion polls show almost 60 percent of the French support same-sex marriage but less that half want to let gay couples adopt children, which is part of the reform.

More world stories from NBC News:

• US drone strikes kill at least 18 Pakistani militants, sources tell NBC
• Assad gives defiant speech as Syrian rebels edge closer to Damascus
• Chavez ally re-elected, cementing position as possible caretaker president
• 'Nobody helped us for an hour,' Indian rape witness says
• 'Strong young woman': Taliban shooting victim Malala leaves hospital
• ANALYSIS: Is peace really in the air in Afghanistan?
• Drug-resistant malaria threatens deadly global 'nightmare'
• From alcohol to kites: An A to Z guide to the Islamic Republic of 'Banistan'

Follow World News from NBCNews.com on Twitter and Facebook

Copyright 2013 Thomson Reuters. Click for restrictions.