THE SNP is heading for "disaster" at the next general election unless it listens to critics inside the party over concerns about Holyrood's gender reform laws, according to a former SNP MSP.

Dave Thompson, who supported Kate Forbes' bid to become SNP leader and is now a member of Alba, issued the warning to his former party after Humza Yousaf won the contest and vowed to challenge the UK Government over its refusal to give royal assent to the Gender Recognition Reform Bill.

Full unlimited access to The Herald is only £2 for 2 months.

👉 Click here to get this offer

Mr Yousaf beat Ms Forbes and Ash Regan, both of whom are opposed to the reforms, in the five week contest which ended yesterday.

Ms Forbes narrowly missed out on the leadership, claiming 47.9 per cent of the vote in the second round, while Ms Regan was eliminated in the first round with 11 per cent of the vote. Some 30 per cent of SNP members did not vote in the ballot.

READ MORE: Humza Yousaf right to challenge veto on gender reforms, insists Black

"I think [Humza Yousaf] needs to look again at issues like the Gender Recognition [Reform] Bill and accept that there needs to be some amendment to it," said Mr Thompson.

"It definitely had an impact on the membership. What it showed was that the SNP establishment weren't prepared to listen to anybody. They just were in their own little echo chamber.

"I think what this result shows is that they totally underestimated the SNP membership and the country as a whole. And a political party which pays no attention to half its own membership and half the country is heading for doom.

"And next year's general election will be a disaster unless Humza takes Kate and Ash on board and people like Joanna Cherry and listens to the arguments in relation to protections of women's spaces and women's rights."

READ MORE: Scottish Labour launch bid to lure voters after SNP leadership rows

Speaking on the same programme on BBC Radio Scotland this morning Mr Yousaf was urged to include his rivals in the leadership race in his Cabinet due to be unveiled later this week.

Both Ms Forbes and Ms Regan have significant government experience, with the former serving as Finance Secretary for three years and public finance minister before that, while the latter was formerly community safety minister - a post she quit in protest over gender reform legislation.

Kirk Torrance - a former Alba Party candidate who advised Ms Regan's campaign - said it would be "sensible" to bring the two former rivals into government.

"I think it would be advantageous and very sensible for Humza to do," he said.

"Both Ash and Kate in his cabinet would be a sensible position for him to take, not least because he does need to unite this party."

Mr Thompson also described the close nature of the result as a "wake-up call" to the SNP.

"Half their members and more than half the country don't agree with them, therefore they've really got to start thinking about holding out the hand of friendship, to take Kate and Ash into the cabinet."

Describing Mr Yousaf as a "friend of mine", Mr Thompson added: "He needs to pull in other people."

It is unclear if either candidate would serve in government when asked, with both being coy when asked on Tuesday.

Ms Regan told broadcasters she had not been asked to serve, while the Finance Secretary said: "Humza has won, so it's for Humza to appoint his cabinet and I, like any other MSP, look forward to supporting him in any way possible."

The legislation makes it easier for a transgender person to change their legal gender by lowering the age from 18 to 16, shortening the length of time a person is required to live in their acquired gender and removing the need for a medical diagnosis of gender dysphoria by allowing people to self declare their gender. The UK Government vetoed the bill over fears it would clash with equalites laws, which are reserved.

While the gender reforms were passed in Holyrood with MSPs across the chamber supporting the legislation, surveys of Scottish voters suggest the public is not on board with the changes proposed.

A poll in December found that around two thirds of Scots opposed the central pillars of the legislation.

Research by YouGov for The Times found that voters were most sceptical about lowering the age threshold with 66 per cent opposed. This included 63 per cent of SNP voters, 67 per cent of Labour voters and 75 per cent of Liberal Democrats, despite all three parties backing the bill at Holyrood.

The Scottish Conservatives was the only party to oppose the reforms, though its MSPs were allowed a free vote with some of the party's MSPs voting to support the bill.