LONDON - Gordon Brown is set to face tough questions on Tuesday, just hours after one of the Labour party's most senior officials quit in another fund-raising scandal.

As officials admitted Brown would be "embarrassed" by the latest party funding furore, the Prime Minister is set to face the Westminster press corps at his monthly news conference.

More bad news for Brown came in the shape of an opinion poll on Tuesday that put Labour in its worst position for almost two decades.

The ComRes Poll for the Independent gave the Tories a commanding 13 point lead, enough to give them a majority if an election were held now.

It came after a torrid week that included the tax department admitting it lost the child benefit records of 25 million people, continuing fallout from the Northern Rock credit crisis and stinging criticism from five former defence chiefs over funding for the armed forces.

On Monday, Labour was left reeling after its General Secretary Peter Watt resigned following the revelation that a property developer broke party funding rules by giving hundreds of thousands of pounds in donations without revealing his identity.

Watt, in charge of party finances, said he had been aware of David Abrahams' arrangement to give almost 600,000 pounds in donations to Labour via "gifts" through friends and associates.

Under electoral law, people making donations on behalf of others must give full details of the donor.

"I was aware of arrangements whereby David Abrahams gave gifts to business associates and a solicitor who were permissible donors and who in turn passed them on to the Labour Party, and I believed at the time my reporting obligations had been appropriately complied with," Watt said in a statement.

Opposition parties said it was a return to the sleaze that had blighted former Prime Minister Tony Blair's later years in office, in which it was alleged that titles and peerages were awarded in return for donations.

Acting Liberal Democrat leader Vince Cable told BBC Television the government needed to "clean up" fundraising.

"It is a wholly sleazy area," he said.

Shadow Chancellor George Osbourne said questions about the "murky affair" remained unanswered.

The chairwoman of Labour's National Executive Committee, Dianne Hayter, admitted the affair would leave Brown "saddened and embarrassed".

"(Watt) has been committed, as has the Labour Party, to openness and transparency," she told Sky News, adding the error was "greatly regretted".