Ms Bain had claimed that prosecutors involved in the malicious prosecutions did not understand the law, The Times reports.

Eight years ago, she assisted the lawyers representing David Whitehouse and Paul Clark, who were accused of various offences in relation to the takeover of the club by businessman Craig Whyte.

She had been appointed to deal with a row over documents taken during a raid of Duff & Phelps’s offices in August 2013. The firm’s services had been employed when the Ibrox club fell into administration

The firm said its documents contained “legally privileged materials” that police were not permitted to inspect and demanded they be returned. The Crown Office insisted police were permitted to look at them until Ms Bain secured a bill of suspension and a review of the police search warrant.

Messrs Whitehouse and Clark were cleared of any wrongdoing and paid £21 million after the Crown Office admitted they had been the victims of a malicious prosecution.

In 2019, Ms Bain submitted an affidavit to the Court of Session in Mr Clark’s case against the police and former Lord Advocate, James Wolffe QC.

She expressed criticism of the advocate depute in the case, as well as the deputy head of the serious and organised crime division and a senior fiscal in the economic crime unit.

She said they failed to understand the law of legal privilege in Scotland and found “deficiencies in the originating search warrant and the failure on the part of the police to take steps to protect privileged material”.

In the affidavit, Ms Bain said: “I was surprised at the time that [staff] thought that the issue of legal privilege could be resolved by the police reviewing the materials … Staff were adamant that the police could review the material, and that the law on privilege was different in Scotland than in England.”

The advocate depute, however, rejected the view that the documents enjoyed privilege and supported the view of staff that “the rules on privilege were different in Scotland than they were in England”. Ms Bain, however, said they “had not fully grasped the importance of legal privilege”.

Russell Findlay, the Scottish Conservatives’ community safety spokesman, said Ms Bain must recuse herself from further investigation. He said: “This would also preclude her from consideration of the associated criminal allegations made by Mr Whitehouse.”

A Crown Office and Procurator Fiscal Service spokesman said: “The previous Lord Advocate, James Wolffe QC, made a statement in the Scottish parliament and committed the Crown to further public accountability and a process of inquiry once all litigation has concluded.”

He added: “It is common for lawyers involved in litigation to have differing views and legal arguments are best understood in the full context of proceedings.

“There is an independent legal team and senior counsel advising on these cases.

“The Crown is committed to further public accountability and a process of inquiry once all litigation has concluded.”