Margaret Beckett wrote on Friday to David Cameron urging him to explain the source of loans to the Tories under Michael Howard. She demanded he reveal the names of wealthy individuals and companies, the amounts they loaned – and whether any are foreign. Unless he followed Labour and the Liberal Democrats in giving full details of lenders, his party’s credibility would be “seriously compromised”, she wrote. In the letter Beckett claimed she was “concerned” at the refusal to publish a list of lenders or to confirm whether any of the party’s cash came from foreign sources.

“I am sure you will recognise that failure to do so would seriously compromise your party’s credibility and remove all legitimacy from any call you made to argue the case for openness and reform to the system… We understand that some of these loans may have been given on the basis of confidentiality. But it is clear that the public interest in outlining the full extent of loans received, as we have done, is sufficiently strong to justify any such undertakings you have given being overridden.”

Guido can reveal that Ms Beckett operated a secret trust in the late 90s to finance her leadership ambitions (people forget she was, after John Smith’s death, once leader of the Labour party). The secret “Margaret Beckett Research and Administration Trust” was the conduit for anonymous donations to support her leadership ambitions, it operated in the late 90s but was closed down by 1998 after Blair won the election. In 2000 such trusts became illegal.

UPDATE : Guido has now received an official statement from Margaret Beckett in reply to this letter.