The widow of one of Labour's former major donors, the late Lord Hamlyn, has promised to give the party �1m.

Lady Hamlyn's donation is believed to be the biggest donation that Labour has received in more than a year from a single donor.

Chief fundraiser Lord Levy has admitted his party is in urgent need of funds - its overdraft stands at more than �5m, matched by a �5m mortgage on its new London headquarters.

But, as he revealed details of the latest donation, he told the Times newspaper he was confident the party would be attracting "serious money" in the coming months.

Memorial plaque

Lord Levy told the paper he resented how such large donors had previously been "beaten up" in the media.

"If someone wants to express their belief in a political party by writing out a cheque, why should they be precluded from so doing?"

It is understood Lady Hamlyn asked for her gift, which will be paid in two instalments, to be used to help pay off the party's mortgage on the new Westminster headquarters at Old Queen Street.

Lord Hamlyn gave �1m to Labour before 2001 election

And a plaque will be placed there in memory of her late husband, a millionaire publisher, who gave the party �1m before the last general election.

He died in August 2001.

Since his donation, gifts to the party on that scale have all but dried up while the trade unions have reduced their contributions.

Lord Levy told the paper that allegations of sleaze had made it more difficult to attract money.

He has now resumed his role as the party's chief fundraiser after focusing on his role as Tony Blair's personal envoy to the Middle East.