Liam Fox last night faced the prospect of a fresh investigation into his relationship with best man and self-styled adviser Adam Werritty over claims that Mr Fox failed to declare donations to the House of Commons.
Labour MP Nick Smith has written to John Lyon, the Parliamentary Commissioner for Standards, claiming Mr Fox "may have committed several breaches" of both the Commons code of conduct and the Political Parties, Elections and Referendums Act.
Mr Fox quit as Defence Secretary nine days ago after a string of allegations about the role Mr Werritty played by his side during 17 months in government. Mr Werritty described himself as an adviser to Mr Fox, including on business cards, and attended meetings with senior figures who included Israeli diplomats, a Sri Lankan MP and defence firms, who considered him an aide to the minister.
Sir Gus O'Donnell, the Cabinet Secretary, said in his report on the affair that Mr Werritty's travel was funded by Pargav, which received private donations from Oceana Investment, Jon Moulton, G3 Ltd, Tamares, IRG Ltd and Michael Davis. None was declared. Under Commons rules, MPs must declare any "financial or material benefit in support" of their role, which includes the "services of a research assistant or secretary whose salary, in whole or in part, is met by an outside organisation or individual".
In his letter to the Commissioner, Mr Smith said: "At the very least, Dr Fox appears not to have declared a donation in kind. There are also outstanding questions about the source of some of the funding... Clarification of the precise nature of these sources of funding may lead to further questions about the permissibility of the donors involved."
Mr Lyon is already investigating Mr Fox over expenses claimed for a flat shared with Mr Werritty.