Sheridan 'owned up back in 2002 that he had gone to swingers' club'

Alan McCombes, 51, said it was as far back as 2002 that Mr Sheridan had admitted attending the club, and he had insisted it would never become public.

He declared himself a hostile witness at Mr Sheridan's defamation action in the Court of Session but was ordered to answer questions by the judge.

He told the jury of his fears that the court battle between Mr Sheridan, MSP, and the News of the World - he described it as a "squalid little squabble" - could destroy their party. And he rejected as "absolute nonsense" a suggestion by Mr Sheridan's QC, Richard Keen, that he had played a part in the political assassination of his former leader because he and his lover, the MSP Carolyn Leckie, had wanted to take over at the top.

Mr McCombes was jailed for three days in the run-up to the case for refusing to hand over party documents to the court - Mr Keen called it an "alleged martyrdom" and a "pale imitation" of the prison term Mr Sheridan had served in the 1990s during poll tax protests.

Mr Sheridan is seeking 200,000 damages, claiming he was defamed in articles in the News of the World in 2004 and 2005. The paper maintains that the allegations - that he had affairs, visited Cupids, a swingers' club in Manchester, and had a sex party in a Glasgow hotel - were true.

Mr McCombes was cited as a witness by the News of the World. He said he was in court "under the strongest possible protest" because the paper symbolised everything he stood against as a socialist, and he did not want to take sides in the "bizarre pantomime".

He told the jury he and Mr Sheridan, with others, had been co-founders of the SSP and he was the party's press and policy officer.

In October 2004, the News of the World carried a story headed "Married MSP is spanking swinger" which did not identify anyone, but the SSP called an emergency executive committee meeting to discuss it.

Mr McCombes was questioned by Michael Jones, QC, for the paper, about talking to Mr Sheridan before the meeting, but he referred repeatedly to minutes of the meeting. The judge, Lord Turnbull, had to order him to answer.

Mr McCombes said that about 2001, he asked Mr Sheridan about allegations then circulating that he had attended a club in Manchester. Mr Sheridan denied it. Then, in 2002, the subject was raised again. This time, Mr Sheridan admitted going to the club but said it would never get into the public domain.

At the executive committee meeting, Mr Sheridan had admitted going to the club but wanted to continue to deny it publicly because he believed there was no proof. The members voted that he should resign as leader.

Mr McCombes said he had not wanted to surrender the minutes of the meeting for the court case. He was jailed in May and spent three days in prison.

But the party voted to produce the minutes and he was released.

He insisted the vote to have Mr Sheridan resign was difficult for everyone at the meeting. "There was not one person who was not extremely saddened, because everyone recognised Tommy as the most popular, eloquent and charismatic leader in Scotland, possibly the UK. It would be absurd to take that decision unless there were very, very powerful reasons," Mr McCombes said.

"The idea we fabricated these minutes, framed up Tommy Sheridan, perverted the course of justice, and we are now defending this monstrous frame-up is, frankly, preposterous."

The hearing will resume on Monday.