Rory Stewart has denied claims that he previously spied for MI6 - but acknowledged he could not admit to being a spy even if he had been.
The Tory leadership hopeful was this morning asked about revelations in The Telegraph that he was recruited by the Secret Intelligence Service after graduating from Oxford University.
This newspaper reported claims from a Whitehall security source, who said that Mr Stewart had spent seven years as a spy before entering Parliament.
Asked about the claims on Tuesday, the International Development Secretary told BBC Radio 4’s Today programme that he had “served my country” but if asked whether he was a former intelligence operative, “I would say no”.
Mr Stewart, 46, has faced questions for years about whether he served in MI6, where his father Brian was second in command as its Assistant Chief from 1974 to 1979.
The claim first surfaced in the New Yorker magazine in 2010, when the journalist Ian Parker wrote that Mr Stewart “certainly was” a spy during his early career as a diplomat working in Indonesia and Montenegro.
He is now the bookies’ second-favourite to become the next prime minister after a surge in support following his appearance in a TV hustings event on Sunday night.
Mr Stewart served briefly as an infantry officer in the Black Watch before university and then joined the UK diplomatic service, with postings in Jakarta, Indonesia, and as the British representative to Montenegro in the wake of the Kosovo crisis.
He was the coalition deputy-governor of two provinces in southern Iraq following the 2003 invasion.