THE Tories will today name the rich benefactors who secretly lent the party £20 million as Scotland Yard widened its inquiry into the alleged sale of political honours.

David Cameron, the Tory leader, bowed to mounting political pressure and agreed to a demand by the Electoral Commission for complete transparency. The Tory lenders will move to the centre of the police investigation along with the dozen businessmen who lent the Labour Party £14 million.

Only Mr Cameron, Francis Maude, the party chairman, and Jonathan Marland, the treasurer, know the names of the backers, some of whom have already converted their loans to donations, which will be reported to the commission in the next quarter.

The police have already written to Labour’s lenders demanding to see all documents and e-mails relating to loan transactions. The paper trail is so extensive that the six-strong Specialist Crime Directorate, which is leading the inquiry, has expanded to include another senior officer. The unit’s strength is expected to rise to ten in the next two weeks.

Downing Street is becoming increasingly alarmed by the potential for political damage to the Prime Minister, who has privately described the controversy as “ghastly”.

One No 10 source said: “This is a nightmare. This is going on and on. There is immense frustration about this and appropriate embarrassment about the whole loans situation and how it was handled. We cannot seem to get people to talk about anything else.”

The team of investigators, based at Scotland Yard, is gathering documents from the Labour Party, the House of Lords Appointments Commission and individual donors.

One police source said that the inquiry was delicately poised between the demands of the media and politicians, and was being directed by John Yates, the Deputy Commissioner of the Metropolitan Police.

“To say that officers are sensitive about this one is an understatement. Everything that the police do and say might be used as a rod to beat up the Met. It is very much a case of ‘softly, softly’ and ‘let’s get this one right’,” the source said.

The size of the loans will be disclosed by the Conservative Party today but not the repayment terms. The loans include £1 million from Robert Edmiston, a Midlands car importer whose nomination for a peerage by the Tories was blocked. He has converted it to a donation. Mr Edmiston has been assured that his peerage will go ahead after he resolved a tax dispute.

Lord Laidlaw of Rothiemay, who is based in Monaco, sold his conference business for almost £800 million and has lent about £2.5 million. Others include Michael Hintze, a philanthropist, who lent £2.5 million through a Jersey-based trust a week before the general election; Johan Eliasch, a Swedish sports equipment tycoon who counts Björn Borg and the Duke of York among his friends and made a £1 million loan through Millcentro, a British investment company; Lord Ashcroft, the former Tory party treasurer, who has already come forward with details of a £3.5 million loan; Lord Steinberg, the founder and chairman of Stanley Leisure, the casino operator; and Henry Angest, a banker, who lent about £1 million.

A Tory source said that the lenders were not reluctant to come forward as they sympathised with Mr Cameron’s plight. “They want to help as they know this mess is not of his doing,” the source said.

The police inquiry was started in response to a complaint by Scottish and Welsh nationalist MPs that Labour had broken the Abuse of Honours Act 1925, which outlaws the sale of honours. The inquiry was extended to the Conservatives after complaints from Labour MPs.

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