The published details, accessible by any of the many millions of Facebook users around the world, were immediately removed once authorities were alerted by the newspaper's enquiries.

Security breach denied

David Miliband, Birtain's foreign secretary, made light of the incident and denied there had been a security breach, giving Sawers his full support.

"It's not a state secret that he wears speedo swimming trunks," Miliband said. "For goodness' sake, let's grow up!" Miliband told the BBC.

But security experts remained shocked.

"It is a most distressing and unfortunate security lapse that will take a great deal of money to put right," Professor Anthony Glees, director of Buckingham University Centre for Security and Intelligence Studies, said.

Glees said that the children may now require an additional security detail and that the family may need to move to a new home.

The incident is one of a series of security blunders that have embarrassed the government of Gordon Brown, coming less than two weeks after the British prime minister launched Britain's first national cyber security strategy.

The Mail on Sunday, which published the story on its front page and pictures on a double-page spread, said the information "could potentially be useful to hostile foreign powers or terrorists."

Several government officials called on the government to launch an inquiry into the matter and have since questioned whether Sawers was the right man for the job.