Stephen Flynn has called for a “full post mortem” into the SNP’s Rutherglen & Hamilton West by-election defeat, saying the party must be frank about the problems it faces. 

The SNP’s Westminster leader said it would be unwise “to try and downplay the scale of the challenge that faces us as a result of this”. 

He said there was a need to “re-inspire” SNP supporters after the party’s widely publicised internal problems, which have included dissent over policy at Holyrood, independence strategy and a police probe. 

“A lot of our vote just didn't come out and we need to reflect upon that,” he said.

However he denied Humza Yousaf was in trouble.

READ MORE: Rutherglen and Hamilton West: Labour score historic victory

The SNP suffered a drubbing at the hands of Labour in the marginal seat, seeing its share of the vote fall slump as Labour won with 58.6% on a 20.4% swing.

Scottish Labour leader Anas Sarwar said the win for candidate Michael Shanks was “seismic” and showed Scottish politics had “fundamentally changed”.

The by-election was caused by local voters ousting former SNP MP Margaret Ferrier in Scotland’s first recall petition after she broke Covid rules during lockdown.

She won in 2019 with a majority of 5,230 and a 44.2% vote share to Labour’s 34.5%.

Mr Shanks won with a majority of 9,466 after outpolling the SNP’s Katy Loudon two-to-one.

Speaking on BBC Radio Scotland, Mr Flynn admitted it had been a “bruising night”, and congratulated Mr Shanks on his win.

He said: “As an element of context, obviously everyone's very well aware of Margaret Ferrier and the problems that she caused in terms of breaking Covid rules, they’re very well aware of the challenges that the party’s faced internally over the course of this year. 

“But I don't think it would be reasonable or wise of us to try and downplay the scale of the challenge that faces us as a result of this. 

“And as such, I think the party needs to come together as a collective, reflect on the result and try to make sure that we have a clear path to victory next year.

“When you do lose by the margin by which we lost, I  think it's important for any political party who's in that position to reflect upon what went wrong. 

“It's only been a few hours since the result was cast. It’s a bit too early to do that full post mortem. But I think it’s necessary, the party needs to do and we need to do it quickly.”

The Aberdeen South MP said his party had no control over Tory and Liberal Democrat voters switching to Labour, but it could address SNP switchers to Labour and SNP voter apathy.

He said: “What we can control is the fact that some of our vote went to the Labour Party, but a lot of our vote just didn't come out and we need to reflect upon that and find a way of making sure that we re-inspire folk to vote for the Scottish National Party and I think that’s a challenge that we face.”

Reflecting on his own election in 2019 after regaining a seat the Tories won in 2017, he said: “I know what it's like to lose as an SNP member, and what it’s like to win as an SNP member.  And I want to make sure that we get back to winning next year.”

Asked if Mr Yousaf, who narrowly won the SNP leadership contest in March, was in trouble, Mr Flynn said Alex Salmond hadn’t been considered in trouble after the SNP lost the 2013 by-election for the Holyrood seat of Dunfermline to Labour.

READ MORE: Rutherglen and Hamilton West result - John Curtice reacts

Reminded Mr Salmond didn’t have open dissent in his ranks or been forced to suspend Fergus Ewing for indiscipline, Mr Flynn said: “I don’t think that the First Minister is in any trouble whatsoever. 

“He’s had a lot to deal with internally in the party. I think the public are very well aware of that. I think he's done a remarkably good job in that regard. 

“I hope that when we go into conference, because party conference is only ten days or so away in Aberdeen, that the First Minister is in a position to reassert why voting for the SNP is so important, and I’m confident he’ll be able to do that.”