MI6 Chief's Facebook blunder

But Mr Miliband denied that national security had been compromised, saying it was "no state secret" that the MI6 chief wore Speedos on holiday.

And shadow business secretary Ken Clarke said the UK's enemies "did not wholly rely on the Mail on Sunday and Facebook for their information".

Former prime minister Sir John Major also described the issue as "overblown".

Lady Sawers disclosed details including the location of the London flat used by the couple and the whereabouts of their three children and of Sir John's parents.

She put no privacy protection on her account, allowing any of Facebook's 200 million users in the open-access "London" network to see the entries.

Lady Sawers' half-brother, Hugo Haig-Thomas, a former diplomat, was said to be among those featured in family photographs on Facebook.

Mr Haig-Thomas was an associate and researcher for controversial historian David Irving, who was jailed for three years in Austria in 2006 after pleading guilty to Holocaust denial, the paper reported.

Mr Miliband said: "What are you leading the news with that ... The fact that there's a picture that the head of the MI6 goes swimming. Wow that really is exciting.

"It is not a state secret that he wears Speedo swimming trunks, for goodness sake let's grow up.
"This allegation that there's great secrets and then you find out it's about his swimming trunks and the fact that his family's getting dragged into it."

He added: "He was appointed 10 days ago to be the head of MI6; he's an outstanding professional who will do a really good job in an outstanding organisation that does a huge amount for this country.

"The newspapers have gone on to Facebook and got pictures of him in his swimming trunks - the fact that you're leading on it when we've got Iran, Afghanistan and the other issues ..."

Mr Clarke dismissed the potential security implications of the information - which he said he was certain Britain's enemies would have already known.

"In the old days we used to keep the name secret, all photographs were banned and I never really believed that the Russians didn't know who the head of MI6 and MI5 was," he said.

"I suspect that the enemies of this country do not wholly rely on the Mail on Sunday and Facebook for their information so I personally would get a little more calm.

"I strongly suspect that serious enemies of this country will be quite familiar with some of the home life of the head of our security service and I very much doubt whether our national security has been jeopardised."

And Sir John Major said the MI6 chief was a "very able appointment".

"It's pretty unfortunate that this has happened, I think that is true," he told the Andrew Marr Show.
"But I think when you're faced with leaving Iraq possibly too early, huge problems in Afghanistan, the mess in Pakistan, the depth of the recession, I think this falls a long way below those."
The Liberal Democrats insisted that Gordon Brown should call an inquiry.

Foreign affairs spokesman Ed Davey said: "Normally, I would welcome greater openness in Government for officials or politicians but this type of exposure verges on the reckless.

"The Prime Minister should immediately commission an internal inquiry as to whether this has breached the security of the incoming head of MI6 too seriously to allow him to take up the post."

Mr Mercer, chairman of the counter-terrorism sub-committee, told the paper that Sir John was in a "very sensitive position".

He said: "As a long-serving diplomat and ambassador, his whole family have been involved in his line of business for decades. I would have hoped they would have been much more sensitive to potential security compromises like this."

PA