Ex-Scottish Socialist Party leader Tommy Sheridan asked the party's treasurer to lie for him in the days after he admitted visiting a swingers' club, she told the politician's perjury trial.
Alison Kane, who has since left the party, said Mr Sheridan asked her to lie to her members of the party - and persuade other members of its committee to get rid of minutes detailing his confession.
The 42-year-old said Mr Sheridan had been "one of my best friends". But their friendship ended after she told the party's executive what he had asked her to do, she told the High Court in Glasgow on Tuesday.
Mr Sheridan and his wife are on trial for perjury following his defamation trial against the News of the World in 2006.
Ms Kane was a member of the executive committee that Mr Sheridan told he had twice visited Cupid's club in Manchester. After the emergency meeting, in the party's offices in Stanley Street, Glasgow, she said he was left "fighting for his political life" but "had lost the plot".
She told the court: "He wanted me to meet with the press and say lies about other people. Tommy was aware of the minutes and he asked me to 'rattle some cages' so no minutes were produced. He wanted for them not to be produced - for me to suggest to other people that we should lose those minutes. Tommy wanted any minutes to disappear - for there to be no minutes.
"We haven't spoken since. I saw that he was putting himself above the movement. I thought he had lost the plot by that stage. It broke my heart to do it. I realised the course of action Tommy was proposing would destroy our party. It would make it unelectable."
Under cross-examination from Maggie Scott, QC, appearing for Mr Sheridan, Ms Kane said the party was in debt to the tune of £176,000 at the time the allegations about Mr Sheridan were made, but denied that the former MSP was put under pressure to step down as convener so the party would not have to pay for the libel action he intended to take against the tabloid.
Earlier, the jury was told that Scottish Socialist Party members did not want to hand minutes of the meeting to court officials because it would have "dropped Tommy in it".
Barbara Scott, who took the minutes at the November 9, 2004 meeting, said a citation asking for the documents was sent to the party's headquarters ahead of Mr Sheridan's civil defamation action.
Ms Scott told the court the SSP was reluctant to hand over minutes of the meeting. She said: "The party didn't want to hand them over because they would have dropped Tommy in it."
Ms Scott had not seen the minutes since late November 2004 when she had handed them in to the party.
However she said there had been talk of changing minutes and she decided she wanted to get them back. They were returned to her after she asked for them.
The court heard she was a witness in the earlier civil case and was cross-examined by Mr Sheridan. She said: "He said I had fabricated the whole minutes after the fact as part of a conspiracy against him."
Mr Sheridan denies lying to the courts during his case, which followed the newspaper's claims that he was an adulterer who had visited a swingers' club.
It is alleged he made false statements as a witness in the defamation action on July 21, 2006.
He also denies another charge of attempting to persuade a witness to commit perjury shortly before the 23-day legal action got under way.
Mrs Sheridan denies making false statements on July 31, 2006, after being sworn in as a witness in the civil jury trial at the Court of Session in Edinburgh.
The trial, before Lord Bracadale, continues.