Prime Minister John Key's participation in a "prison rape" stunt on music radio station The Rock is making world headlines.

Photo: Supplied

United Kingdom newspapers The Times and The Guardian, as well as US broadcaster CNN, are among those that have reported on Wednesday's incident, in which Mr Key agreed to get into a cage in The Rock's studio. He was then asked to pick up a bar of soap - a reference to rape in prison.

Most of the foreign media reports focused on the stunt being the latest of a number of incidents in which Mr Key has raised eyebrows. They mentioned "blunders", including the recent furore in Parliament over his attack on Labour for "backing the rapists", in response to opposition accusations that the government had been weak in its dealings with Australia over the detention of New Zealanders on Christmas Island.

The Times said the prime minister had "come under fire after appearing to make light of rape while taking part in a crude radio station stunt".

"The Rock stunt is the latest in a series of live radio appearances Mr Key has taken part in in which he has revealed more personal information than many New Zealanders might wish to know," the article said.

The newspaper also called attention to New Zealand's record of sexual violence: "In the 2011 United Nations Report on the Status of Women, New Zealand was ranked worst of all the OECD countries for rates of sexual violence," it said.

CNN also reported Mr Key was "under fire", for participating in a "prison rape" joke. The broadcaster listed a number of instances of earlier "unstatesmanlike" behaviour under the heading "Media blunders".

It linked it to his "you back the rapists" comments which resulted in a walkout by female MPs, the much-publicised incidents in which he pulled a waitress's ponytail and his personal revelations about urinating in the shower, which he made during an earlier radio appearance.

The Guardian ran a story under the headline "New Zealand prime minister John Key criticised for 'rape joke' stunt".

Photo: The Rock

The story included quotes critical of Mr Key's actions from Massey University lecturer Deborah Russell who said by playing along with rape jokes the prime minister was making light of sexual violence.

"This makes me feel ill. When the PM thinks it's okay to participate in rape jokes, how can women feel safe?" she tweeted.

Rae Duff, the national president of the National Council of Women, was quoted as saying Mr Key was routinely "trivialising" sexual violence.

Other international media outlets to feature the prime minister's comments were the Daily Mail and the International Business Times.

A spokesperson for Mr Key told The Guardian, "The prime minister does these interviews in the spirit of Christmas and the content is decided by the hosts.

"The interviews are meant to be light-hearted, and the prime minister hopes the media and the public take them that way."

Petition to strip Key of White Ribbon role

Meanwhile, Auckland psychotherapist Kyle MacDonald has started an online petition to remove Mr Key as ambassador for White Ribbon, a global campaign by men who condemn violence against women, over the comments.

The petition has received more than 7000 signatures.

Launching the petition, Mr Kyle wrote, "I have become increasingly concerned about the actions of our prime minister, and how they show a complete lack of understanding about the impacts of sexual and physical violence in this country."

His "prison rape" joke on radio yesterday was the last straw.

"I believe it is no longer OK for John Key to make light of sexual abuse and sexual violence, and so I ask you to join me in calling on the White Ribbon organisation to remove John Key as an ambassador."

Ken Clearwater, of Survivors of Sexual Abuse New Zealand, said he found the stunt "bloody appalling".

"Rape is not a joke, full stop. Regardless of the gender of the victim. The psychological damage done to men and boys is the same as to women," he said.

Mr Clearwater called for Mr Key to apologise.

"Obviously he didn't give it a lot of thought before he went into it, and that's probably a major issue we have in this country - we talk about the 'rape culture' and obviously he thinks that rape is a joke and that's really scary."

Mr Clearwater says he has been interviewed by The Guardian about Mr Key's radio stunt.