UK PM laughs off 'selfie' at Mandela service

US President Barack Obama (R) and British Prime Minister David Cameron pose for a picture with Denmark's Prime Minister Helle Thorning Schmidt. Photo / AFP

British Prime Minister David Cameron has laughed off criticism that he had acted inappropriately by posing for a mobile phone "selfie'' with US President Barack Obama at Nelson Mandela's memorial service.

A photograph of Cameron and Obama leaning in and smiling broadly for a smartphone snap taken by Danish Prime Minister Helle Thorning-Schmidt has caused a storm on social media.

Asked about the picture din the House of Commons, Cameron quipped that "you should always remember that the television cameras are always on''.

The Conservative leader also joked that he was building political bridges, a reference to Thorning-Schmidt's marriage to the son of Neil Kinnock, the former leader of the Tories' arch-rivals Labour.

In a tongue-in-cheek question, politician Martin Horwood noted EU efforts to abolish expensive mobile phone roaming charges.

"Has the prime minister had the opportunity to discuss international mobile phone usage with any European heads of government in the last day or so?'' he asked.

To laughs in the chamber, Cameron replied: "You could say in a roundabout way, and, er, perhaps in my defence, you should always remember that the television cameras are always on.

"But in my defence I'd say that Nelson Mandela played an extraordinary role in his life and in his death in bringing people together.

"And so of course when a member of the Kinnock family asked me for a photograph I thought it was only polite to say yes.''

Earlier, Cameron's spokesman said there had been "plenty of words'' from the prime minister and other world leaders celebrating Mandela's life and achievements during the service at Soweto's World Cup stadium on Tuesday.

"What the media may choose to report is a matter for yourselves and your colleagues,'' the spokesman told reporters.