The man who filmed a video which allegedly shows Tommy Sheridan admitting he visited a swingers club has defended the recording.
Socialist Tommy Sheridan says the tape has been doctored
George McNeilage, the best man at Mr Sheridan's wedding, insisted the tape was not a fake.
He said he made the video because the politician had turned his back on activists in his political heartland of Pollok, Glasgow.
The Scottish News of the World has published more claims from the tape.
The paper alleges it shows Mr Sheridan admitting he visited a swingers' club with a Danish former colleague and his brother-in-law.
Mr McNeilage, who still lives in Pollok, said the politician's decision to sell his story to another tabloid in July after his libel victory over the News of the World prompted him to release the tape.
Mr Sheridan was awarded £200,000 after the News of the World printed allegations about his private life.
The former activist claimed he was angered after Mr Sheridan branded his former Scottish Socialist Party (SSP) colleagues "scabs" for testifying against him in court.
"I was gobsmacked that Tommy had done this," Mr McNeilage said.
Mr McNeilage told the BBC's Politics Show the tape was made on a camcorder in his home in November 2004.
He claimed he decided to record Mr Sheridan after he refused to discuss his resignation with activists "who had helped to create him".
'Broke my heart'
He said his "comrades", who helped Mr Sheridan rise to prominence during the anti-poll tax campaign in the 1990s, had suggested making the recording.
Mr McNeilage said the tape's contents "broke my heart" and he decided not to show them.
Mr Sheridan insists the tape is a fake.
His former friend is adamant that it is real, saying: "This is a 40 minute tape with a fluent conversation where I break into his speech, where he breaks into my speech and there's no way it could be doctored up."
He added: "Tommy went from being a man of integrity to a man of a million lies."
George McNeilage claims the conversation was taped in 2004
He refused to disclose how much the News of the World paid for the tape.
He said the sum was "ironic" compared to the amount paid to Mr Sheridan by the Daily Record after he won his defamation case.
The first transcripts were released last Sunday by the News of the World.
Commenting on the latest accusations, Mr Sheridan - who has since gone on to found a new left-wing party called Solidarity - said: "Another Sunday, another pack of lies.
"The News of the World's attacks on me and Solidarity continue.
"To be attacked by the same reactionary forces that called striking miners 'scum' and striking firefighters 'Saddam's stooges' is a badge of honour."