Defence Secretary Liam Fox has ordered an investigation into continuing claims surrounding the role of a controversial friend and adviser.
The Ministry of Defence confirmed that Dr Fox had asked his most senior official, Permanent Secretary Ursula Brennan, to look into what he describes as "baseless allegations" concerning Adam Werritty.
In recent days Dr Fox has been accused of putting national security at risk by allowing Mr Werritty - a former flatmate who was best man at his wedding - access to the MoD, even though he is not employed by the government.
The Guardian reported that Mr Werritty had joined the Defence Secretary on an official visit to Sri Lanka, despite Dr Fox having previously said that Mr Werritty did not travel with him on official visits overseas.
In a statement, Dr Fox said: "A number of baseless accusations have been made in recent days.
"For the sake of clarity I have asked my Permanent Secretary to establish whether there has been any breach of national security or the Ministerial Code. She will report back in due course."
Mr Werritty has been a controversial figure in Whitehall. Despite having no official role he is reported to hand out business cards with a portcullis logo describing himself as "adviser to Rt Hon Liam Fox MP".
Labour MPs have questioned his access to the MoD after it was disclosed in parliamentary answers that he had visited Dr Fox there 14 times in the space of just 16 months.
The latest claims concern his presence during an official visit by Dr Fox to give a lecture in Sri Lanka in July.
The Guardian has published a photograph of Dr Fox arriving for the lecture which, the paper said, showed Mr Werritty in the background. The MoD confirmed that Mr Werritty was present for the event although it said that he was not part of the official party.