The wife and father-in-law of former Glasgow MSP Tommy Sheridan are expected to be charged with perjury, a source close to the family has told the BBC.
Mrs Sheridan gave evidence during her husband's case
It is understood Gail Sheridan and her father Angus Healy have been invited to attend a police station on Tuesday.
Mr Sheridan was charged with perjury last December in connection with the damages case he won against the News of the World in 2006.
Three other people have also been charged over the case.
Former MSP Rosemary Byrne, 59, Jock Penman, 58, and Graham McIver, 39, all face perjury charges after being arrested over the past week.
Mrs Sheridan and Mr Healy were key witnesses for Mr Sheridan, who left the Scottish Socialist Party to form Solidarity, when he won £200,000 in damages from the newspaper.
The case focused on a series of lurid allegations the paper made about Mr Sheridan's private life.
During the case, witnesses gave conflicting evidence about the circumstances of the allegations.
Two months after the proceedings concluded, prosecutors ordered police to carry out a criminal investigation into allegations of perjury.
A source close to Mrs Sheridan and Mr Healy said the pair are expected to be charged with perjury when they attend a police station in Edinburgh for questioning on Tuesday.
Solidarity spokesman Jim Monaghan earlier confirmed that Ms Byrne had been charged with perjury.
The party also said that Mr Penman and Mr McIver had been charged with perjury, although Lothian and Borders Police said they were unable to confirm the charge.
Mr Monaghan said: "We consider this to be nothing more than a political witch-hunt."
He said Ms Byrne would not be speaking publicly on the matter, but added that she had co-operated fully with the police investigation.
"She [Ms Byrne] went voluntarily to the police station, was interviewed and cautioned and was released afterwards," said Mr Monaghan.
Ms Byrne is co-convenor of Solidarity and it is understood that Mr Penman is a member of the party.