The Scottish Conservatives have submitted a motion of no confidence in Deputy First Minister John Swinney at Holyrood.
Both Labour and the Greens said they will back the vote if legal advice remains unpublished and therefore unavailable to the committee investigating the botched handling of harassment complaints about Alex Salmond.
The Tories say Swinney has failed to comply with two parliamentary votes calling for the publication of legal advice received by the Scottish Government.
With the backing of all three the opposition parties, the advice will have to be published or the vote will likely be successful.
Swinney, who is also the education secretary, would then be expected to offer his resignation.
The advice relates to Salmond’s successful legal challenge of the government’s harassment complaints procedure, which led to the former first minister being awarded more than £500,000.
A one-line motion was submitted with parliamentary authorities on Monday, with the Conservatives aiming for a debate on Tuesday afternoon.
They hope to secure the publication of the legal advice before Nicola Sturgeon appears at a Holyrood committee on Wednesday.
In December, Swinney said he was keen to find a “practical way” to hand over the evidence to the committee examining the government’s handling of harassment complaints, but no such arrangement has yet been made.
“We gave John Swinney one more opportunity to respect the will of the Scottish Parliament.”Douglas Ross
The Tories say they will withdraw the vote if the government publishes the legal advice.
The Scottish Conservative leader, Douglas Ross, said: “We gave John Swinney one more opportunity to respect the will of the Scottish Parliament. He has failed to do so.
“Opposition parties have united twice already to demand the legal advice is released. We now call on them to do so a third time.
“We are still willing to withdraw this motion at any point, if the government respects the will of the Scottish Parliament and publishes the legal advice.”
Anas Sarwar, the new Scottish Labour leader, said his party would support the motion if the advice remained unpublished.
Speaking to the media before the Tories lodged the motion of no confidence, Sarwar said: “John Swinney has got an opportunity to hand over the legal advice that parliament, by a clear majority, has demanded of him on two occasions.
“And if he fails to do so, he is deliberately thwarting the work of a parliamentary committee, he is deliberately acting against the will of parliament, and we would have no choice but to vote against him in a vote of no confidence in that circumstance.
“So the ball is in his court, it’s up to him whether he’s going to do what’s asked of him by parliament, or whether he’s going to force us to vote against him in a vote of no confidence.”
If the motion goes to a vote, it would be the second time in less than a year that Swinney would face such a debate on his position.
In August, he survived a no-confidence vote thanks to the backing of the Scottish Greens.
Other opposition parties supported the motion due to Swinney’s role in the scandal surrounding estimated pupil exam grades.
A spokesperson on behalf of Scottish Green MSPs said: “The Scottish Greens have previously voted to ensure that the Government’s legal advice is made available to the committee inquiry, and this remains our position.
“The committee on the Scottish Government Handling of Harassment Complaints has made it clear that it needs access to the Scottish Government’s legal advice on its investigation into Alex Salmond to fulfil their remit, and parliament has repeatedly backed the committee.
“The Scottish Government now has just days left to agree the terms of the committee’s access to the information requested. Reaching an agreement on this which is acceptable to the Committee is clearly the only way to avoid a vote of no confidence.
“The Conservatives have been shameless opportunists throughout this process, but the Scottish Greens will always defend the integrity of the Scottish Parliament and its ability to hold government accountable.
“This inquiry should be focused on identifying what went wrong with the investigation into sexual harassment, and on the interests of the women who were failed by the process and others who will need to have confidence in the complaints process in future.”
A Scottish Government spokeswoman said the committee had already seen “detailed evidence” on its legal position at all key points during the judicial review.
The spokeswoman said earlier: “If there is a need [for] further information, the Scottish Government stands ready to discuss that with the committee.
“We are conscious that we must enable the committee to fulfil its remit without creating a general waiver of legal privilege that could limit the ability of future Scottish Governments to request and receive candid legal advice in future litigation.”