Lobbyist Adam Werritty is today being questioned for a second time by officials investigating his links with Defence Secretary Liam Fox.
It is understood the self-styled adviser to Dr Fox is being interviewed by a senior Cabinet Office official away from Whitehall amid fresh allegations over how he was able to fund his jet-set lifestyle.
Officials are expected to work through the weekend as they seek to complete the investigation headed by the Cabinet Secretary Sir Gus O'Donnell.
David Cameron has said that he will wait until he has received Sir Gus's report before deciding whether Dr Fox should lose his job.
Meanwhile, The Times reported that Mr Werritty's trips following Dr Fox around the globe staying in some of the world's most luxurious hotels were paid for by Pargav Ltd - a not-for-profit company which he set up.
According to the paper, £147,000 was paid into the firm's bank account. Among the donors were said to be a corporate intelligence company with a close interest in Sri Lanka and a property investor who lobbies for Israel.
Earlier this week, Dr Fox told the Commons that although Mr Werritty - his best man and former flatmate - had joined him on 18 overseas visits since he became Defence Secretary, he was "not dependent on any transactional behaviour to maintain his income".
A spokesman for one of the reported donors to Pargav - the investment company Tamares Real Estate - confirmed today that it had paid £3,000.
Tamares is owned by Poju Zabludowicz, the chairman of BICOM - an organisation which promotes understanding of Israel in Britain.
The spokesman said that Mr Zabludowicz had made the payments in order to support Pargav's work promoting peace in the Middle East - including arranging round table dialogues.
He said that Pargav appeared to be a continuation of one of Mr Werritty's previous companies, Security Futures which was dissolved last year.
"Poju made a contribution to Security Futures for its peace promotional work and the latest invoice came in from Pargav. He understood it to be a continuation of that organisation's activities," the spokesman said.
Pargav is listed as having an office in Goswell Road in Clerkenwell, north London, although there appears to be no telephone number listed.
According to The Times, Pargav's sole director is Oliver Hylton - a charity adviser to the CQS hedge fund and a former director of Security Futures.
CQS's chief executive, Michael Hintze, is reported to have given Mr Werritty a desk and telephone line at the firm's London offices to run another organisation, Atlantic Bridge, which was wound up earlier this year after losing its charitable status.
Mr Hylton told The Times that Mr Werritty had asked him to become a director of Pargav in June last year.
"He came into my office and said I want to set up a new company. It sounds ridiculously naive in hindsight but I agreed. I signed the documents and nothing more," he said.
He added that he had regarded Mr Werritty as "an advisor of some sort" to Dr Fox.
"Anything he did was for the good of Liam Fox and supporting his office," he said.
Former cabinet secretary Lord Armstrong of Ilminster said that Dr Fox's links with Mr Werritty raised questions about his judgment, but in the end it would be a "political judgment" by Mr Cameron as to whether he should keep his job.
"The question marks seem to be over Dr Fox's judgment in relying so much on Mr Werritty after he became Secretary of State for Defence, and how much he knew about Mr Werritty's background and his financial arrangements," Lord Armstrong told BBC Radio 4's The World at One.
"We are told by the Ministry of Defence that he wasn't either an official or an unofficial adviser, but that doesn't seem quite consistent with what happened. There are questions of judgment about Dr Fox."
Labour MP John Mann called on Dr Fox to resign this weekend.
The Bassetlaw MP said: "It's time for Fox to trot. Dr Fox is diverting the Government from dealing with the vital issue of the economy.
"Dr Fox should do the right thing and resign over the weekend."