A leading gay Tory has donated £20,000 to the campaign to elect Boris Johnson as Mayor of London.

Nick Boles was the frontrunner to be his party’s candidate for Mayor until he withdrew from the race after being diagnosed with a form of cancer.

Now it has emerged that he is among a list of donors to Boris’ campaign, alongside property developers, hedge fund managers, lobbyists and art dealers.

The donations, totalling £234,000, have been registered with the Electoral Commission.

Labour MPs have called on the House of Commons standards commissioner John Lyon to investigate why they have not yet appeared in the Register of Members’ Interests.

A spokesman for the Boris campaign said that they had taken advice from the standards commissioner that campaign donations do not have to be registered.

Lord Marland, who is chair of the Boris campaign as well as a former Tory party treasurer, said he expects to raise in excess of £1m. He has personally donated £15,000.

Lib Dem candidate Brian Paddick’s campaign has set a fundraising target of £150,000.

Last week’s dinner with Elton John and other potential supporters will have added to his fighting fund – the other significant fundraising event sop far, with party members, raised £5,000.

The £400,000 limit on spending for Mayoral campaigns only applies to the seven week period leading up to polling day on May 1st.

Incumbent Mayor and Labour candidate Ken Livingstone is expected to receive substantial financial support from the trade unions and is also planning some novel fundraising events such as a fish and chips dinner and a quiz night.

Nick Boles came within 500 votes of winning Hove in the 2005 election.

He will fight the constituency of Grantham and Stamford for the Conservatives at the next election.

The Tory nomination became vacant when sitting MP Quentin Davies defected to the Labour party just before Gordon Brown took office as Prime Minister.

Mr Boles was a strongly-tipped candidate for the Tory nomination for Mayor of London, but withdrew in July when he was diagnosed with Hodgkins Lymphoma, a type of cancer.

He told PinkNews.co.uk in October that he does not regret pulling out of the race, despite returning to full health much sooner than expected.

“I feel that in life some things are meant to happen and other things aren’t – Boris was meant to be selected.

“If you were writing a TV script you would write Boris as the candidate to take on Ken.

“Perhaps I was meant to take the nomination for Grantham and Stamford.”