The SNP must avoid a lurch to the right under the “extreme” views of Kate Forbes, the party’s former deputy Westminster leader has warned.

Mhairi Black, who stepped down as an MP at the general election, called on the SNP to get its own house in order after her party's devastating defeat on July 4.

She will lift the lid on life at Westminster as part of an hour-long debut comedy show at the Fringe in August, including drunkenness in the voting lobbies and archaic traditions.

Ms Forbes, who is a member of the Free Church of Scotland, provoked anger in the SNP in last year's leadership election when she said she would have voted in Holyrood against gay marriage and that she believed having children outside marriage was "wrong".

READ MORE: 'Too close to Sturgeon': John Swinney faces calls to resign

However, she later softened her stance to say she would not change the law on gay marriage if she became First Minister.

She lost out to Humza Yousaf in the 2023 leadership contest to succeed Nicola Sturgeon.

Mr Yousaf was forced to stand down as SNP leader and First Minister in April and was succeeded by John Swinney in May who made Ms Forbes Deputy First Minister in an effort to unite the party and put more on a focus on economic issues.

Ms Forbes had been considering entering the 2024 leadership race but opted not to do so saying the approach Mr Swinney had set out in his pitch for the top job aligned with her own.

READ MORE:  Kate Forbes: 'SNP has to change' after election defeat

However, Ms Forbes's return to Cabinet was not universally welcomed by those on the socially progressive wing of the SNP such as Ms Black.

Interviewed by the Sunday Post, Ms Black said: “We all remember Kate Forbes’ interview where she said she wouldn’t have supported gay marriage and doesn’t think people should have kids out of wedlock.

(Image: PA) Former SNP deputy leader at Westminster Mhairi Black.   Photo PA.

“Basically really archaic and, in my opinion, quite extreme views.

“That is out of step with what the SNP has stood for and where the SNP has attracted so much support. It’s because it has been this progressive force.

READ MORE: Kate Forbes rules herself out of SNP leadership contest

“It has been wanting to take Scotland into the 21st Century and wanting to be inclusive.

“If you then start endorsing the sort of views Kate Forbes was saying voluntarily, on camera, then that’s a massive red flag to so many people – particularly young people.

“The truth is independence won’t happen without young people and certainly support for the SNP and success for the SNP won’t happen without young people on board.”

Asked what advice she would have for the new First Minister, Ms Black said he must get “real and brutal” about what needs to change in the SNP.

READ MORE: Kate Forbes: SNP must rebuild trust of Scottish voters

She said: “I think a lot of the SNP’s woes in the past few years have been internal rather than external things happening to them.

“Basically the party needs to get its house in order and that’s not going to happen unless there is real commitment to it and the leader is making it happen.”

She said not enough was done to improve the structures of the party to make it fit for purpose under the increased membership, with problems being brushed “under the carpet”.

“Anything that’s uncomfortable, let’s not talk about it,” Ms Black said.

“All that breeds is resentment, disappointment and disillusion. I think that is the basis for a lot of the difficulties that the party has had.”

In March last year, during the leadership contest, Ms Black said Ms Forbes becoming the next First Minister could risk splitting the SNP.

Speaking on The Bunker podcast at the time, she insisted that Ms Forbes’ views on social issues had been “damaging” for the party.

Asked if Ms Forbes becoming SNP leader would split the party, she said: “Honestly I don’t know, to tell you the truth.

“It’s very much a wait and see what happens. I wouldn’t even want to risk that, that’s why I’m backing Humza.

“I think he’s the best person to be able to band folk together again.”

Ms Forbes has repeatedly come under pressure over her personal moral and religious views which are seen as out of step with her party's stance on some social issues.

However, when she was appointed Deputy First Minister in May she insisted she would accept collective Cabinet responsibility, meaning she would support party policy.

Last month she voted in favour of the final stage of legislation to create "buffer zones" outside abortion clinics in Scotland.

The bill put forward by the Scottish Greens MSP Gillian Mackay will not allow anti-abortion protesters to demonstrate within 200m outside healthcare services.

The move is designed to stop patients and staff from being intimidated.

Commenting on Ms Black’s remarks, an SNP spokeswoman said: “The SNP has consistently been a moderate, left-of-centre political party that is resolutely focused on delivering for the people of Scotland.

“Whether it’s free prescriptions, free tuition or the game-changing Scottish Child Payment, we are determined to build a better Scotland and work towards Scottish independence.

“Our key priorities of eradicating child poverty, promoting economic growth, ensuring our public services are sustainable and tackling climate change are also those of people across Scotland, and we are committed to delivering on those priorities.”

The SNP suffered a humilating defeat at the general election winning nine seats - down from 48 in 2019.

The result has led to calls within the party for change.

Earlier this month former health secretary Alex Neil said Mr Swinney should stand down as leader in favour of Ms Forbes and Westminster SNP leader Stephen Flynn as the party prepares for the Holyrood election in 2026.

Both Ms Forbes and Mr Flynn have backed Mr Swinney remaining as SNP leader and First Minister, while Mr Swinney said after the election result the party needed to win back the trust of voters.

Speaking in Edinburgh on July 5 after a devastating night for the party, the First Minister said he took full responsibility for the campaign.

“The Scottish National Party needs to be healed and it needs to heal its relationship with the people of Scotland, and I am absolutely committed to doing that,” he said.