SNP Westminster leader Stephen Flynn has backed Nicola Sturgeon retaining her membership of the SNP as a police probe into the party’s funding continues.

With the former first minister having become the third person to be arrested as part of Police Scotland's investigation, Humza Yousaf has faced calls to suspend Sturgeon from the party from both members of the SNP as well as opposition parties. 

But with Sturgeon having been released pending further investigation by the police without any charges having been brought, Flynn defended the decision by Yousaf to keep her within the party.

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The SNP Westminster leader said: “If someone is charged by the police for wrongdoing, they shouldn’t be in the Scottish National Party.

“I am not aware of anyone being charged by the police in relation to any matter who is in the Scottish National Party.”

Speaking on BBC's Good Morning Scotland programme, he added: “If that changes, I am sure people will act accordingly.”

SNP MSP Michelle Thomson however has been among those calling for Sturgeon to resign from the party whip while the police investigation is ongoing.

Thomson argued that she herself had needed to do this while an MP in 2015, despite not being “personally under investigation” and “certainly not arrested”.

Flynn refused to comment on that, saying: “Circumstances in the past are not something I can answer for. I wasn’t part of that decision-making process."

His comments came after Sturgeon insisted she had “done nothing wrong” when asked if she should step back from the SNP.

Yousaf meanwhile has insisted that “natural justice” means his predecessor should remain in the party.

With no charges currently having been brought, he said there was “no reason” for Sturgeon’s membership, or that of her husband Peter Murrell or former SNP treasurer Colin Beattie to be suspended.

Sturgeon, Murrell, who was until recently chief executive of the SNP, and MSP Beattie have all been arrested by police as part of what has become known as Operation Branchform.

All three were released without charge pending further investigation.

Meanwhile, according to a poll Sturgeon has seen her popularity fall by 38 points since February – when she announced she was quitting as SNP leader and first minister – to minus 18.

Flynn however hailed Sturgeon as an “incredibly talented politician”.

He said: “I think it goes without saying that Nicola Sturgeon over a long period of time was someone who won election victory after election victory because she was an incredibly talented politician.”

Asked if she was, as Yousaf had insisted, the “most impressive” politician in Europe, the MP added: “I think over the course of her tenure undoubtedly.

“I don’t think anyone credible would argue otherwise, indeed I think many of her opponents would say the very same thing.”