Portillo: This is not a trivial matter

"We were discussing here whether the fact that Mr Ecclestone gave �1m to the Labour party had been the key factor in the Labour government changing its policy on tobacco advertising, much to the benefit of the motor racing industry."

The allegations are contained in a new book by political writer Andrew Rawnsley of The Observer, extracts of which are published in the Daily Mail.

The row centres around an interview on the Today programme in November 1997, in which Mr Brown appeared to deny any knowledge of the donation.

The book alleges that he admitted privately afterwards that he had lied, saying: "If this gets out, I'll be destroyed."

Mr Portillo said Mr Brown's version of events did not tally with comments made by his official spokesman on the Today programme on Tuesday.

Mr Portillo said the spokesman said Mr Brown and Mr Blair had discussed the Ecclestone donation on a Friday in the back of the prime minister's car in 1997.

Bernie Ecclestone had his donation returned

"On the following Monday John Humphries asked the chancellor of the exchequer about the Ecclestone donation," he said.

"He said he wouldn't know if there was a donation until he saw the lists published just like any other member of the public, that he didn't know the truth of the matter and that he hadn't been told."

Mr Portillo said the chancellor was a critical part of the government and may have been party to the decision over the donation.

"He said that he did not know the true position that he hadn't been told and that he would know whether there was a donation when he saw the lists published just like any other member of the public," he added.

He wants to smear the chancellor - that is part and parcel of what he is all about

Alistair Darling

Social Security Secretary Alistair Darling also defended Mr Brown, accusing the Conservatives of trying to smear him.

"I can understand why Portillo is seeking to do this. He wants to smear the Chancellor - that is part and parcel of what he is all about," he told the Today programme.

And Education Secretary David Blunkett said the government deserved to get credit when it got things right.

"In the end it will be inflation and unemployment, it will be the ability of our nation to read and write and add up and it will be what we do with the health service on which we should be judged."