The Conservatives have been accused of attempting to evade election law after the party admitted it had repaid £5m in secret loans, including cash from foreign backers.
The party reignited the row over funding as it published details of £16m still owed to wealthy supporters, but confirmed it had repaid money to anonymous backers, some of whom were not registered to vote in Britain.
Senior Tory officials said the number of anonymous lenders was "in single figures" and refused to give further details. Tory sources also admitted that one of its public lenders, Dame Vivien Duffield, although a UK citizen, lived abroad and was not registered to vote in Britain.
They insisted that the loans were all on commercial terms and within the law. They also pledged to open the party's books in full to watchdogs from the Electoral Commission.
But Labour claimed the disclosure proved the Conservatives had attempted to side-step legislation banning political donations from overseas.
Ian McCartney, the Labour Party chairman, said: "The Tories have finally been forced to admit that their election campaign was bankrolled by foreigners. This Labour Government outlawed foreign donations to prevent those from outside this country interfering with our democracy.
"By failing to provide these details, the Conservatives and David Cameron are fuelling suspicions that they have even more to hide. All we know - and David Cameron has confirmed this - is that any embarrassing loans have been hurriedly repaid in the hope that the donors can remain hidden."
But a Tory spokesman retorted: "We have given far more disclosure about our loans than Labour. They should not throw stones. They have only given a list of a few select individuals."
However, yesterday Francis Maude, the party chairman, admitted he regretted accepting loans from overseas.
He told the BBC: "These loans represent a very small part of our financial backing. I wish we had not done so... We have repaid these loans and I hope the matter is perfectly clear. It would clearly have been better if we had not, as things have turned out."
Earlier he said: "No-one who has supported us in recent years has done so under any self-interest. We have not been for a long time a party that looked like it was about to be the next Government. The people who have backed us have done so out of conviction, out of their belief that Britain needs to have a party that is capable of being an alternative to the Labour government."
David Cameron, the Tory leader, will meet Tony Blair on Tuesday to try and negotiate a solution to the loans row which has tarnished both major political parties.
Yesterday's disclosure by the Conservatives follows the announcement on Thursday that Scotland Yard's probe into the alleged sale of honours has been widened to become a "cross-party investigation".
The Conservatives attempted to draw a line under the rumbling row over party funding yesterday.They published a list of 13 major supporters who still have outstanding loans worth £16m to the party.
The party also said it had recently taken out a bank loan for nearly £16m to buy the freehold on its former headquarters in Smith Square which, together with the next door property, was now worth more than £30m.
A spokesman said: "David Cameron has done the best he could possibly do in this situation. He wants to get to the situation where all of our loans are disclosed publicly and if we cannot disclose them publicly they will have to be repaid."
Conservative officials insisted that all loans were on strictly commercial rates. They declined to give details of repayment terms but said the Electoral Commission would be able to see details in confidence to confirm they were within electoral law.
Four key individuals, Lord Ashcroft who lent £3.6m, Lord Laidlaw of Rothiemay, who lent £3.5m, Johan Eliasch, who lent £2.6m, and Michael Hintze, who lent £2.5m bankrolled the party with loans totalling £12.2m.
A fifth major lender, the millionaire car importer Robert Edmiston, last week revealed he was converting a £2.1m loan into a donation. His donation was declared by the party yesterday along with all other gifts of £50,000 or more since January.
Lord Rennard, chief executive of the Liberal Democrats, said: "It's now for the Electoral Commission to satisfy themselves that these, or other, loans were on properly commercial terms.
"In future there should be proper transparency over significant loans, as well as significant donations."
Where the money came from
* Lord Ashcroft (lent £3.6m)
The former Tory treasurer, and its most generous donor, was made deputy chairman of the party three months ago. He was awarded a peerage in 2000 by William Hague.
* Lord Laidlaw of Rothielay (£3.5m)
Irvine Laidlaw founded the world's largest events and conference company. It was sold last year for £768m. Ennobled in 2004 on the recommendation of Iain Duncan Smith.
* Johan Eliasch (£2.6m)
The tycoon made his fortune from sports equipment. Born in Sweden but recently became a British citizen. He includes Prince Andrew among his friends.
* Michael Hintze (£2.5m)
Received a reported £60m pay packet from CQS Management, a London-based hedge fund. Was made Knight Commander of St Gregory by Pope Benedict XVI.
* Victoria, Lady de Rothschild (£1m)
The former wife of Evelyn de Rothschild, with whom she has three children. American-born, she was a Tory fundraiser for five years.
* Raymond Richards (£1m)
Wealthy Manchester businessman, now deceased. The party is repaying the loan to his estate.
* Henry Angest (£550,000)
Anglo-Swiss banker who is chairman and chief executive of Arbuthnot Banking Group. Estimated to be worth £40m. The 65-year-old was a declared backer of David Davis for the leadership of the Tory party, alongside several other Conservative-leaning millionaires. Lives in Chelsea. Lists his recreation as dendrology - the study of woody plants and trees.
* Cringle Corporation Ltd (£450,00)
A Manchester-based property and letting company.
* Lord Steinberg (£250,000)
Betting tycoon who is chairman of Stanley Leisure, with an estimated worth of £98m. One of Britain's biggest political donors, he backed Kenneth Clarke in the Tory leadership race. Was made a peer in 2004.
* Dame Vivien Duffield (£250,000)
One of the richest and most high profile philanthropists in the arts world. She is the daughter of Sir Charles Clore, and chairs the Clore Duffield foundation, which has given more than £8m to the arts since 1998.
* Charles Wigoder (£100,000)
An entrepreneur who made his name in the fledgling mobile phone industry in the early 1990s. Now chief executive of Telecom Plus.
* Alan Lewis (£100,000)
A former party treasurer who lectures at the Oxford School of Management. Also former chairman of the CBI initiative for Europe.
* Graham Facks-Martin (£50,000)
A retired farmer who is also a prominent Conservative councillor in north Cornwall.Reuse content