LONDON - Labour will not accept donations made by a property developer through intermediaries, because they were not properly declared and were illegal, Gordon Brown said Tuesday.

He told reporters he had known nothing about 600,000 pounds donated by David Abrahams and that the money would be returned.

"The money was not lawfully declared so it will be returned," he said at his monthly news conference.

"We will ask senior people to advise on the safeguards that the Labour Party will apply in the future to the receipt and declarations of donations."

On Monday, Labour was left reeling after its General Secretary Peter Watt resigned following revelation of the donations.

Watt, in charge of party finances, said he had been aware of Abrahams' arrangement to give the money via "gifts" through friends and associates.

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

Brown said Watts' resignation had been necessary.

His comments came as he was hit by 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.

Brown hit back at the scandals saying that voters would take a "longer term view".

Earlier 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.