MSPs want witnesses to give evidence under oath in a Holyrood inquiry into how sexual misconduct allegations against Alex Salmond were handled.
Tory Donald Cameron and Lib Dem Alex Cole-Hamilton believe the move is necessary in case there is conflicting evidence.
It came after it was confirmed Salmond and Nicola Sturgeon are both “likely” to be called to answer the committee’s questions.
In 2018, Sturgeon’s government investigated claims of misconduct against Salmond when he was First Minister.
Salmond challenged the Government in court and a judge ruled the internal probe had been tainted by bias and was unlawful.
The debacle cost the public purse over £500,000 and a committee of MSPs was set up to examine key decisions.
The committee’s work was suspended when Salmond was separately charged with sexual offences, but it was kickstarted after the former First Minister was cleared.
Issues to be probed by the committee include the development of the policy that underpinned the Salmond investigation, as well as how the actual complaints were handled.
MSPs are also certain to ask questions about meetings between Sturgeon and Salmond during the Government investigation.
After these meetings were revealed, Sturgeon referred herself to independent advisers to judge whether she had breached a code of conduct.
At a meeting of the Holyrood committee, Cameron said: “My other and main point about evidence is to suggest, and actually request, that the committee should take sworn evidence - evidence on oath.”
He said it was “imperative” that the evidence is as accurate as it could be, adding that the committee would likely receive “conflicting” versions of events:
“Taking sworn evidence underscores the gravity of the subject matter.”
In practice, Cameron said it would mean the committee convener administering an oath or affirmation with each witness.
Cole-Hamilton agreed with the oath call: “We will hear conflicting stories and I think it is vital that we have confidence in what we as a committee hear."
A number of MSPs expressed a desire for the committee to act with speed on the inquiry.
As revealed by the Daily Record, the committee has drawn up a list of potential witnesses.
In relation to how the complaints policy was developed, Permanent Secretary Leslie Evans and deputy First Minister John Swinney were among the suggestions.
On the investigation of the complaints against the former First Minister, Evans, civil servant Judith McKinnon and Salmond himself are believed to be on the list.
On the issues surrounding the ministerial code of conduct referral, Evans, Sturgeon and Salmond are marked as potential witnesses.
Peter Murrell, who as SNP chief executive is also Sturgeon’s husband, and senior party staffer Ian McCann were also mentioned as possible witnesses.
Labour MSP Jackie Baillie said at the committee session: “The First Minister and the former First Minister are likely to be invited.”
Salmond and Sturgeon were once once political allies, but they are no longer close.
The former First Minister has been particularly critical of Evans for her role in the botched investigation.
A Scottish Parliament spokesperson said:
“At its meeting today, the Committee agreed to invite the Permanent Secretary to give evidence to the Committee in mid August.
“The Committee also agreed a list of potential witnesses to invite written evidence from at this stage. This list will be published shortly.
“Over the summer the Committee will be gathering evidence as it begins its inquiry. Letters inviting written evidence will be published when they are issued and submissions to the inquiry will be made available on the Parliament’s website.”
