Phil Walter / Getty Images, file

New Zealand Prime Minister John Key reportedly defended his "gay" remark by saying it was "just a slang term" used by young people.

New Zealand's prime minister has been rebuked by "Lord of the Rings" actor Ian McKellen for joking about a radio host's "gay" sweater.

John Key teased broadcaster Jamie Mackay for wearing a red top instead of blue, the color of his National Party. “You've got that gay red top on there,” Key said in the interview on Friday.

It was reportedly the second gaffe on the same day for Key, who was accused of earlier telling an audience of students that LA Galaxy soccer player David Beckham was "thick as bats***."

Radio New Zealand said Key described Englishman Beckham as handsome and "a really nice guy" but "thick", according to a report in Britain’s Daily Telegraph.

Key refused to comment on the alleged slur on Beckham, but defended his "gay" remark by saying it was "just a slang term" used by young people, according to television news website TZ NZ.

"If someone was offended by it then I apologize but it's not exactly like a term you don't hear everywhere,” he said. "I voted for gay marriage, I'm hardly homophobic. I led the charge on it."

However, McKellen, the British actor and gay-rights campaigner who played Gandalf in the New Zealand-filmed "Lord of the Rings" franchise, said Key "should watch his language."

In a blog post on Monday, he wrote: "I'm currently touring secondary schools in UK, attacking homophobia in the playground and discouraging kids from the careless use of 'gay' which might make their gay friends (and teachers) feel less about themselves. So even as he supports the proposal to introduce same-gender marriages in New Zealand, I do hope John Key listens to his critics and appreciates their concern. Careless talk damages lives."

Australia’s Herald Sun reported that Twitter users criticized Key, calling his "gay" remarks homophobic and his comments about Beckham embarrassing.

Twitter user Guy Williams posted: “John Key is quickly becoming to New Zealand what Borat was to Kazakhstan.”

The Herald Sun also reported that radio host Mackay had dismissed the exchange as "nothing more than harmless banter".

"It's a storm in a teacup... no wonder the media sometimes gets a bad name," Mackay added.

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