At least one of the three Jewish donors to the friend of former Defence Secretary Liam Fox, Adam Werritty, is understood to have voiced serious concerns about where his money went.

The JC has learned that the donor would be prepared to hand over details of any transactions to fraud investigators at City of London Police.

The news follows a demand from John Mann, the Labour MP who has been leading the calls for transparency in the case, for full disclosure by the donors. He said: "If money has been misused by Werritty it is essential that those giving that money clear their good names by giving details to the City of London Police."

Mr Mann told the JC this week that he believed such a move could trigger Mr Werritty's arrest.

This would be deeply embarrassing to the Conservative Party as Dr Fox would almost certainly be questioned in any investigation.

As the JC reported last week, Conservative Party treasurer Howard Leigh solicited money from Jewish donors. Money initially went to Mr Werritty's charity Atlantic Bridge and later to his companies Security Futures and Pargav.

Three senior figures in the Jewish community are known to have given money to Mr Werritty: Mick Davis, chief executive of Xstrata and chair of the executive committee of the Jewish Leadership Council, Poju Zabludowicz, the property billionaire who also chairs Israel advocacy group Bicom, and Michael Lewis, a former vice-chair of Bicom who heads Oceana Investments.

The donors remain furious at the suggestion that they sought out Liam Fox's friend in order to buy influence or access.

The JC approached all three men for comment but none was prepared to make a statement.

Investigations have so far focused on whether Mr Werritty misrepresented himself as a official adviser to Dr Fox. Mr Werritty had two sets of business cards with the House of Commons portcullis logo printed on them. One described him as "advisor" to Dr Fox and the other stated that he was from the "office of Dr Liam Fox MP".

Harvey Boulter, a Dubai-based private-equity boss, has demanded a full police investigation after handing over what he considered to be sensitive information to Mr Werritty, in the belief that he had an official role.

Venture capitalist Jon Moulton has said Dr Fox approached him directly to donate to Mr Werritty. It is thought this revelation is what finally made Dr Fox's position untenable.

Mr Mann is also calling on hedge fund boss Michael Hintze, whose CQS company provided a desk for Mr Werritty for his Atlantic Bridge activities, to declare any concerns he had about the activities of the unofficial adviser