Max Cotton reports on the latest developments between The Times and Mr Ashcroft

The billionaire businessman is categorically denying any suggestion that he has been involved in money laundering or drug dealing in the Central American state of Belize.

In an open letter to the The Times's Editor, Peter Stothard, he accused the paper of taking part in a conspiracy to smear him.

Michael Ashcroft holds dual British and Belize nationality

He insisted: "I do not condone crime, and in particular I do not condone drug trafficking."

He continued by saying there had been "an almost constant stream of inflammatory articles in The Times" about him, Belize and organisations to which he is connected.

He described the articles as "perhaps the most one-sided, partial and coloured account of anyone's affairs ever produced by a newspaper in a free country".

A Conservative Party spokesman said the writ claimed damages against Mr Stothard, the Times's Deputy Political Editor, Tom Baldwin, reporter Toby Follett, and Times Newspapers Ltd.

Mr Stothard, in a written reply to Mr Ashcroft, defended The Times's journalism and said the paper would mount a 'vigorous defence' against the writ.

He added: "Your attempt to connect our reports to the timing of the Eddisbury by-election is absurd."

Parliamentary privilege

The announcement came after one Labour MP used parliamentary privilege - which allows MPs to make statements without fear of libel proceedings - to detail allegations apparently from US agencies' files.

The BBC's John Pienaar: "Mr Ashcroft is accusing his critics of trying to smear him"

Another backbencher dubbed Mr Ashcroft "one of the biggest drug-runners in the West".

Mr Blair was asked at Prime Minister's Questions about his backbenchers' comments.

Peter Bradley: Used parliamentary privilege to make allegations

He replied: "The Conservative Party can refer this entire case to the Neill Committee, so why don't they do so?"

But the Committee on Standards in Public Life, chaired by Lord Neill, does not examine individual cases.

Mr Blair also announced a draft bill on party funding would be presented in the Commons next week to "ban foreign donations and ensure that donations over £5,000 are disclosed".

Mr Ashcroft has denied all the accusations levelled against him and promised to provide a detailed rebuttal of claims made by Labour MPs.

The Conservative Party will not fund their treasurer's legal action, but say they will continue to support him against the "smear campaign".

'Links to drug inquiries' - MP

Earlier in the Commons, Labour's Dennis Skinner claimed the Tories were "receiving £1m a year from one of the biggest drug-runners in the West".

Peter Bradley: "To be caught up in one drugs investigation may just be a matter of bad luck"

Labour MP Peter Bradley also read from files, which he said came from the US Drug Enforcement Agency (DEA), the Federal Bureau of Investigations and the International Narcotics Bureau.

He demanded Mr Hague take action to determine whether any of the allegations stretching over the past decade affected Mr Ashcroft's position within the party.

Mr Bradley said it was "extraordinary" Mr Hague had chosen not to act, despite the "drip, drip, drip" of allegations against Mr Ashcroft.

He suggested the Conservative leader could not afford to challenge his treasurer, who has donated more than £3m to the Tories in recent years and is its single biggest funder.

Conservative MP Christopher Gill, responding to Mr Bradley in the Commons, said: "The House of course will be understanding that what he has said has been said under parliamentary privilege.