Tommy Sheridan, the former leader of the Scottish Socialist party, faces jail for lying during a defamation action against the News of the World in which he was awarded £200,000.
The former MSP was convicted of perjury on Thursday after a 12-week trial at the High Court in Glasgow.
The perjury investigation was launched after Mr Sheridan, 46, won a civil action before a jury in 2006 over the newspaper’s allegations that he cheated on his wife and took part in orgies.
The judge, Lord Bracadale, told Mr Sheridan that when he returned for sentencing next month, he could expect to be given a prison sentence.
His wife, Gail, 46, had also been accused of perjury, but the charge against her was dropped last Friday.
Following the jury’s majority verdict, Alex Prentice, advocate depute, moved for sentencing, giving a short biography of Mr Sheridan’s political career and mentioning previous convictions for breach of the peace.
Mr Sheridan told the jury how he had spent time in jail after his protest against the poll tax and nuclear weapons.
Lord Bracadale requested background reports and said any submissions by Mr Sheridan could be made at the sentencing hearing on January 26.
The judge told Mr Sheridan: “You have been convicted of the serious offence of perjury and must return to court expecting to begin a prison sentence.”
At the start of the trial in October, Mr Sheridan faced 18 allegations, which were reduced by the prosecution to six.
The verdict brings to a close what is thought to be the longest-running perjury case in Scottish legal history.
The court heard from a succession of high-ranking members of the SSP who said Mr Sheridan had confessed to attending a swingers’ club in Manchester on two occasions.
During the second week of the trial, Sheridan released his defence lawyer, Maggie Scott, QC, and opted to represent himself – just as he had done successfully during the 2006 defamation action.
Sheridan always maintained his innocence and claimed there was a vendetta against him.
Speaking outside court, Mrs Sheridan said: “I have and will always stand by Tommy.”
Get alerts on Media when a new story is published