The wife of the new head of Britain's spy agency has posted pictures of her husband, family and friends on Internet networking site Facebook, details which could compromise security, a newspaper said on Sunday.

Sir John Sawers is due to take over as head of the Secret Intelligence Service in November. The SIS, popularly known as MI6, is Britain's global intelligence-gathering organization.

In what the Mail on Sunday called an extraordinary lapse, the new spy chief's wife, Lady Shelley Sawers, posted family pictures and exposed details of where the couple live and take their holidays and who their friends and relatives are.

The details could be viewed by any of the many millions of Facebook users around the world, but were swiftly removed once authorities were alerted by the newspaper's enquiries.

There were fears that the hugely embarrassing blunder could have compromised the safety of Sir John's family and friends, the newspaper said.

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

It was the latest in a string of security blunders, lapses and leaks by British officials that have embarrassed the government of embattled Prime Minister Gordon Brown.

(Writing by Jon Hemming; Editing by Jerry Norton)