I do not see myself supporting the Conservatives or any other party led by somebody who is so keen to go into the euro

Stuart Wheeler

Stuart Wheeler, multi-millionaire chairman of a spread betting company IG Index, insisted he was not seeking to influence party policy with his �5m gift to the Tory war-chest - the largest single donation in British political history.

The betting tycoon also played down newspaper reports that he might double his donation as "very unlikely".

But his comments on which leader he preferred sparked Labour calls for the Tories to give Mr Clarke a shadow cabinet role in order to prove that Mr Wheeler was not buying a say over party policy.

'Too keen on the euro'

Mr Wheeler said he would not give money to the Conservatives or any other party if after the election Mr Clarke or another pro-European became leader.

However he would consider making further donations to the Conservatives if Mr Clarke was made a member of a Hague-led shadow cabinet, he said.

He told the BBC: "I'm very confident that William Hague will remain leader whether he wins or not.

"But if Kenneth Clarke was to become leader after the election, I do not see myself supporting the Conservatives or any other party led by somebody who is so keen to go into the euro."

Foreign Secretary Robin Cook challenged Mr Hague to show he was not influenced by Mr Wheeler's �5m donation by bringing Mr Clarke into his frontbench team.

Mr Cook said it was "entirely wrong that any large donor should say to a party who it is prepared to see as spokespersons for that party".

Robin Cook: Issued challenge

Speaking on GMTV's The Sunday Programme, he added: "In a way, what he said does give Tory leader William Hague the chance to prove that he is for real when he says that he's independent and not influenced by these donations.

"If he wants to prove he really is independent and not influenced by the money coming in from Mr Wheeler, let him bring forward Kenneth Clarke.

"It will do the Tory Party a lot of good. He's the most authoritative, senior, respected figure on the Tory benches."

Speaking on the BBC's Breakfast with Frost programme, Liberal Democrat leader Charles Kennedy said Mr Wheeler's donation was offensive to most people's sense of fair play.

He said: "Should it be for wealthy tycoons to start deciding who becomes the democratically elected leaders of our parties? I don't think so."

'Absolute nonsense'

But shadow culture secretary Peter Ainsworth said reports about Mr Wheeler attaching conditions to his donation were "absolute nonsense".

"Mr Wheeler has made it absolutely clear that there are no strings attached to any of the money that he very kindly and wisely invested," he said.

Kenneth Clarke: "Highly valued"

He added that Mr Clarke was a "very highly valued member of the party" and that "I would be very surprised if anyone could try and keep him quiet".

IG Index was established by Mr Wheeler in 1974.

It introduced gambling on the London financial markets, moving into sports betting and then financial trading.

The company is currently forecasting a Labour election victory and said its founder is going against predictions.

"Stuart doesn't set the book or our odds," said a company spokesman.

"They relate to the current state of the opinion polls and bets that people place with us.

"He is at odds with IG's predictions at the moment, but those odds can change and move and it will be interesting to see how, and if, they do move before the election."

IG is also offering bets on the numbers of seats the main political parties will win at the election and predicts the Tories will secure 212 to 220 seats and Labour 372 to 380.