THE SNP’s co-operation deal with the Scottish Greens is “worth its weight in gold”, Humza Yousaf has said amid speculation over the pact falling under either of his fellow leadership contenders.

Ash Regan has argued that she isn’t afraid of the Greens walking away from the Bute House agreement in the case that she becomes SNP leader and refuses to challenge Westminster over its blocking of Scotland’s Gender Recognition Reform Bill.

Meanwhile, after Kate Forbes said she would have voted against equal marriage in 2014, and suggested having children outside of marriage would be “wrong” for her, concerns were raised over how she could work with the keenly pro-LGBT Greens – while one SNP source claimed the smaller party would immediately quit the deal if she won the election.

Speaking exclusively to the Sunday National, the Health Secretary reiterated his commitment to co-operating with the Greens.

“A minority government, I think, would be disastrous,” Yousaf said. “I’ve been part of a minority government before, you have to battle day by day by day to get your policy and legislation through that Scottish Parliament.

“And that was back then, the political debate and discourse we have now is far more toxic.”

He went on: “The deal with the Greens is to me worth its weight in gold, for a number of reasons.

“In a time when political discourse is divided it shows that parties that have some commonalities, of course, but also some differences can come together in a collegiate manner for the best interest of the country.”

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Yousaf raised the practical challenge of returning to minority governance – and suggested it would have a negative impact on independence campaigning efforts.

He painted a picture of a new SNP leader casting their Green colleagues aside before trying to get MSPs to vote for them to become first minister.

“Now if we become ungovernable, we become unelectable,” he said. “There’s no way that’s going to help us grow the independence movement by any stretch of the imagination. I’m unapologetic and I’m unashamedly supportive of the deal we have with the Greens.”

Regan, who quit the Government last year in protest over the legislation, has prompted speculation over the future of the Green/SNP pact by repeatedly saying she would not challenge Alister Jack’s use of a Section 35 order.

The National: Ash Regan

Current First Minister Nicola Sturgeon had described the Tory government’s move as an “assault on Scottish democracy”.

“I’m not afraid of having a minority government, let's put it that way,” Regan told The National at her campaign launch on Friday. “I think you have to work harder to get things done, but I think it's definitely achievable.”

Meanwhile amid the row over Forbes’s comments last week, the SNP’s policy chief Toni Guigliano suggested that she would “rip up” the Bute House agreement upon entering office.

One source told the Daily Record that the Greens would immediately quit the deal should Forbes become SNP leader.

READ MORE: Kate Forbes stands by view that women should not become ministers

The Greens have suggested that an SNP leader failing to challenge the UK Government over its Gender Recognition Reform block would be a make-or-break moment.

“The UK Government's decision to veto this clearly devolved bill is an abuse of their power" a spokesperson said. "As long-term allies of the trans community, the Scottish Greens agree with the First Minister that this decision must be challenged robustly.

“Not to do so would set a very damaging precedent and would be incompatible with any belief in Scotland's right to self-government."