Former Scottish Socialist Party leader Tommy Sheridan has begun his £200,000 defamation action against the publishers of the News of the World.
Tommy Sheridan arrived at court with wife Gail
Mr Sheridan, who arrived at the Court of Session with his wife Gail, has launched the action over articles by the Sunday newspaper in 2004.
These claimed that the Glasgow MSP had committed adultery, was a "swinger" and had participated in orgies.
He said this was "untrue" but the paper said it was "substantially true".
The News of the World had also claimed that while Mr Sheridan said he was teetotal, he had drunk champagne.
After a jury of five women and seven men had been sworn in, junior counsel Alistair Clark, for News Group newspapers, said the News of the World was a newspaper "which prides itself on campaigns and exposing hypocrisy on the part of public figures".
In his opening speech, Mr Clark said evidence would be heard about a swingers club in Manchester called Cupid's - where people went for casual sex - which Mr Sheridan was said to have visited.
He told the jury they would also hear about a party at a leading Glasgow hotel, where Mr Sheridan was alleged to have been seen having sex with a woman - not his wife.
The lawyer also promised witnesses who would tell about their affairs with the MSP and about a meeting of the Scottish Socialist Party when Mr Sheridan resigned as their leader, saying he wanted to spend more time with his pregnant wife.
Allison Kane, the party's treasurer, was the first witness called
The trial later heard claims that Mr Sheridan admitted visiting Cupid's club on a couple of occasions in previous years with close friends.
The claim came from first witness Allison Kane, 38, who said he made the admission at a private meeting of the SSP's executive on 9 November 2004.
News of the World lawyer Michael Jones QC told the court the newspaper published an article on 31 October 2004, with the headline: Married MSP Is Spanking Swinger.
The article carried details of how an unnamed politician in the Scottish Parliament had allegedly gone to a swingers club, enjoyed threesomes and being spanked by lovers wearing red PVC gloves.
Another article carried claims by News of the World columnist Anvar Khan that she had a "kinky fling" with a married Scottish politician.
'Honest and decent'
The special meeting of the SSP's top brass was called less than two weeks after those allegations were published.
Ms Kane, the party's national treasurer, told the court there was "some concern the article may be referring to Tommy".
She said that after Mr Sheridan left the meeting on 9 November 2004, 19 members of the party's executive voted unanimously to force him to resign.
When Mr Sheridan's counsel, Richard Keen QC, questioned Ms Kane, he said six "honest and decent" members of the SSP had a different recollection of the meeting.
There was no admission from Tommy Sheridan about visiting the swingers' club, said the lawyer.
Instead there was a "cabal" trying to oust him.
The jury heard that the SSP later voted to keep the minutes of the meeting confidential and they were only handed over to the court after one of those present, Alan McCombes, had been found in contempt of court and the SSP reversed their earlier decision.
The trial continues.