A media watchdog has voiced concerns over a nude shot of Mariah Carey on the front of OK! magazine.

The pregnant singer is on the front cover of the latest edition of the celebrity gossip magazine with her belly exposed and her husband, Nick Cannon, covering her cleavage with his hands.

The front cover shot has been criticised by the Safermedia group, which said it was another example of pornography becoming mainstream in media.

The group is asking people to write letters of complaint to the magazine's publishers and the Press Complaints Commission.

Safermedia said the advert "demeans women" and "sexualises pregnancy and motherhood unnecessarily".

It said: "This is an unusually explicit cover for OK! Magazine … and is another example of pornography becoming increasingly mainstream in all forms of the media."

Safermedia is campaigning against what it regards as a sexualisation of mainstream media.

It recently criticised Channel 4 series, The Joy of Teen Sex, for reaching "new depths of sexual explicitness" and promoting risky sexual behaviour among young people.

It also voiced concerns over highly sexualised performances by pop stars Christina Aguilera and Rihanna on X Factor last year, which prompted thousands of complaints to broadcasting regulator Ofcom.

The sexualisation of media and marketing has prompted concern from other corners of society as well.

Last month, a petition was handed to Downing Street by the Mothers' Union, calling on the Prime Minister to bring an end to marketing of a sexualised nature aimed at children.

The British Government is currently undertaking a review into the sexualisation of childhood headed up by Mothers' Union chief executive Reg Bailey.