Cameron is forced to reveal names behind £24m loans

The Conservative party will today disclose the full list of donors who lent the party £24m before the last general election. The list is expected to reveal previously undeclared loans worth more than £12m and at least nine names that have been concealed by the party for over a year.

The Tory leader, David Cameron, has been been forced to release the information as the Electoral Commission, the independent watchdog, demands that the party hand over all contract details of the loans or face court action. The Tories had refused to release the list, claiming that lenders had been promised complete confidentiality. However, it is understood that for the past fortnight the party has privately been seeking to persuade them to be named publicly.

Scotland Yard confirmed yesterday that the Conservatives are also to be investigated over the " loans for lordships" scandal and Jonathan Marland, the party treasurer, will receive a letter asking for information.

The move came yesterday as unrest among Labour backbenchers about their party's hidden £14m loans resulted in a letter to Tony Blair demanding an investigation into whether the party had broken electoral law.

According to Tory sources, Mr Cameron is asking many of those who lent cash to convert the money into donations to prevent the party's balance sheet going deep into the red, making it difficult to attract new cash. The last Tory accounts show the party already had significant loans in 2004 and was not paying commercial rates on an average of £6.8m of loans.

As well as pressure from opponents, the Tories have faced calls from inside the party, including from the shadow attorney general, Dominic Grieve, and former treasurer Lord McAlpine, to make the list public.

Nearly half of the benefactors who gave loans to the Tories have already emerged. The biggest known loan so far is £3.5m from Lord Ashcroft, the party's chairman, who never kept it a secret.

Michael Hintze, a hedge fund millionaire, revealed last Saturday that he had given £2.5m loan last year. On Monday, Robert Edmiston, a wealthy Midlands car dealer, announced he had lent the party £2m which he was converting into a donation. City bankers Arbuthnot Latham, whose directors include major Anglo-Swiss donor Henri Angest lent £2m, while £1m came from Johan Eliasch, a Swedish sportswear magnate.

Meanwhile, Labour MP Bob Marshall-Andrews has formally complained that his party appears to have broken election rules, and has called on Tony Blair as leader to investigate.

In a letter to the prime minister, he said it appeared that Labour's last accounts "may not in fact be totally correct" because loans worth £14m were kept secret until this month.

He alleges that the Labour party should have declared to the Electoral Commission any loans made after the accounts were closed in December 2004 because, under accounting rules, they would constitute "a material event" which, if kept secret, would present a false picture of the party's finances.

The letter also asked Mr Blair to investigate how many loans were taken out between January 1 last year and June 30 2005, the date the accounts were filed with the Electoral Commission, and what the loan arrangement was with each donor.

He also wants to know what details of the loans were made available to the party's auditors, Horwath Clark Whitehill, before they signed off the accounts on June 30 last year. He has asked Mr Blair to explain whether the auditors wanted the information included as a note on the accounts.

Yesterday the MP said: "Until these questions are answered, the party will haemorrhage support from the public and the prime minister will haemorrhage support from within the party. A raft of thoroughly decent voters are going to walk away from us."

Mr Marshall-Andrews has the support of a growing number of backbenchers who want to get to the bottom of the scandal. These include not only members of the leftwing Campaign group but also former ministers and some supporters of the chancellor, Gordon Brown, who was not informed of the loan arrangement.