The fate of Scotland’s First Minister could be decided by a single MSP after the Scottish Greens confirmed to STV News that they would vote to oust Humza Yousaf.

The Scottish Conservatives announced at midday that they would submit a vote of no-confidence in the FM, expected sometime next week.

On Thursday afternoon, Patrick Harvie told STV News that his party would support the no-confidence motion and vote to oust Yousaf.

It comes after the SNP leader ended the historic Bute House Agreement with the Greens and sacked the party’s two leaders from government.

Harvie and Lorna Slater reacted furiously to the news, accusing Yousaf of being “weak and thoroughly hopeless”.

Furious Greens ‘can’t trust weak and thoroughly hopeless’ Humza Yousaf

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They said he had caved in to “backwards forces” within his party and accused him of “betrayal” and “political cowardice”.

“Precisely because the Greens supported Humza Yousaf on the basis of his commitment to the Bute House Agreement, those progressive policies but also a constructive way of working together set out in that agreement,” Harvie said.

“That’s why we supported him, he’s abandoned that, and I think it is appropriate now that if a motion of no confidence is selected by the presiding officer the Greens would support it.”

“Humza Yousaf has signalled that when it comes to political cooperation, he can no longer be trusted”

Lorna Slater, Scottish Greens co-leader

Labour and the Liberal Democrats have already committed to voting with the Tories on the no-confidence motion.

The Greens’ support would bring the total number of MSPs voting against Yousaf to 64 out of Holyrood’s 128 seats, excluding the presiding officer who must remain neutral.

Single MSP could hold the balance of power

That means the key, and ultimately deciding vote, could come down to Yousaf’s former SNP leadership rival Ash Regan.

The Edinburgh Eastern MSP was formerly part of the SNP but defected to Alex Salmond’s Alba Party in October – becoming its first and only elected member.

In that case, presiding officer Alison Johnstone will step in and vote with the status quo, saving the First Minister.

If Regan votes against Yousaf though, that would amount to 65 votes against the SNP’s 63 MSPs, and the FM would lose.

How will Ash Regan vote?

It’s a non-binding vote, meaning Yousaf doesn’t have to quit, but it would send a powerful message and damage his ability to govern.

Asked by STV News whether she would vote for or against her former colleague, she said she had not yet decided.

She said: “First of all, we don’t know what the substance of this is going to be, it’s a bit early to say, I’ll have to look at what comes out.

“But I am in the process of writing to Humza today and in that letter I’m asking him to say how he is going to be progressing independence, how he intends to defend the rights of women and children and also how he is going to return to competent government.”

She said her decision would ultimately depend on “what Humza’s answers to those are”.

She added: “To be honest, it was long overdue that the SNP got rid of the Greens.

“I’m grateful now that Green extremism has been banished from the Government and hopefully this will signal a return to competent government which I think is what all of Scotland is looking forward to over the next few weeks.”

Asked if Yousaf will be answering First Minister’s Questions this time next week, Regan said: “I think we’ll have to wait and see won’t we?”

The First Minister’s spokesperson refused to say whether the First Minister would quit if he lost a no-confidence vote.