The man set to take over as head of Britain's external spy agency has been left exposed after his wife published photographs and family details on the social networking website Facebook, the Mail on Sunday newspaper reported.
The alleged security lapse prompted politicians to demand an inquiry into whether or not the Facebook details had compromised Sir John Sawers, who is relinquishing his assignment as Britain's ambassador to the United Nations to take over as head of MI6 in November.
One politician as "verging on the reckless" since been removed, described the Facebook postings by his wife Lady Shelley Sawers, which have.
The postings, put up on the open-access London network, reveal that Sawers' brother-in-law is a former British diplomat who is now an associate of the controversial Austrian historian David Iriving, who was jailed in 2006 for denying the Holocaust and "glorifying the Nazi Party".
The postings show Shirley Sawyers' half-brother Hugo Haig-Thomas holidayed with John Sawyers last month.
The foreign affairs spokesman for the Liberal Democrat Party called on British Prime Minister Gordon Brown to launch an inquiry into whether the Facebook disclosures had compromised Sawyers' ability to take up his MI6 post.
"Normally, I would welcome greater openness in government for officials or politicians but this type of exposure verges on the reckless," the Mail on Sunday quoted Edward Davy as saying.
"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."