David Cameron's hopes of drawing a line under the scandal surrounding Liam Fox were dealt a blow as Westminster's sleaze watchdog announced he will conduct a fresh probe into the former defence secretary's links with close friend Adam Werritty.
Standards Commissioner John Lyon will look into a complaint from Labour MP John Mann that Mr Werritty was allowed to live in a flat funded from Dr Fox's parliamentary allowances and to run the Atlantic Bridge charity from the MP's Commons office.
The announcement of Mr Lyon's inquiry came just hours after Mr Cameron attempted to brush off questions from Ed Miliband about the affair by telling the Labour leader he was jumping on a bandwagon that had already stopped.
Dr Fox apologised to the Commons for allowing the distinction between his ministerial responsibilities and his personal friendship with Mr Werritty to become "blurred".
In a personal statement, he accepted the conclusion of the report by Cabinet Secretary Sir Gus O'Donnell that he had breached the ministerial code of conduct and recognised he should have listened to civil servants' warnings about the nature of his association with his friend.
He acknowledged it was a "mistake" to attend a meeting with Mr Werritty and a potential supplier without an official being present. And he told MPs: "I would like to say again that I am very sorry to all my colleagues here in the House and to all those who feel let down by the decisions that I have made...
"The ministerial code had been found to be breached and for this I am sorry. I accept that it is not only the substance but perception that matters and that is why I chose to resign. I accept the consequences for me without bitterness or rancour."
Mr Cameron's official spokesman declined to comment on whether Dr Fox might ever return to the Cabinet. Earlier, the PM was challenged by Mr Miliband to give a "categorical guarantee" that no other ministers were relying on unofficial advisers.
The Labour leader said the facts revealed in Sir Gus's report were "deeply worrying", but failed to tell the full story about Dr Fox's links with Mr Werritty, who met him a total of 40 times at the MoD's Whitehall HQ or on trips abroad.
Mr Cameron told him: "You seem to have failed to have noticed that the minister in question has resigned. You're just a bit late."