ALEX Salmond has said today that under Nicola Sturgeon's leadership the SNP would suspend people "at the drop of a hat" as her predecessor as former first minister and party leader entered the debate about why Humza Yousaf had not withdrawn the whip from her following her arrest.

The former first minister said he believed Mr Yousaf had acted "correctly" in not removing Ms Sturgeon as a party member pointing out there is a "presumption of innocence".

However, he noted the approach taken towards Ms Sturgeon was in contrast to other parliamentarians who had had the party whip removed in previous years when she was leader and her husband Peter Murrell was SNP chief executive.

Mr Salmond resigned his SNP membership in August 2018 after it emerged that police were investigating allegations of sexual misconduct against him. He had not been arrested when he quit the party and was later cleared of all charges after a trial.

READ MORE: Nicola Sturgeon should resign SNP membership, says Ash Regan

"Humza Yousaf has set a perfectly defensible line, the presumption of innocence. You don't suspend people until they are charged with something and that hasn't happened as yet," Mr Salmond told Sky News.

"His difficulty is of course it that wasn't the position adopted by Nicola Sturgeon or Peter Murrell, the chief executive and her husband, when they were in power.

"They used to suspend people at the drop of a hat basically. So Humza's difficulty is not the position he's taken, which is a perfectly respectable, defensible, I actually think is the right decision. His problem is is that it's been compared with a whole litany of other people who feel quite rightly they have been treated unfairly in comparison, in their cases some years ago."

During the same interview Mr Salmond did not agree with Mr Yousaf's description of Ms Sturgeon as the "best politician in Europe" which the First Minister made yesterday and added that Mr Yousaf needed to make his own mark.

READ MORE: Nicola Sturgeon arrest: SNP MSP demands clarity on removal of whip

"Humza really has to depart from the previous administration. He's got to have a clear line of departure as the new first minister on what he's going to do from what came before," he said.

"The SNP is under a substantial financial cloud. It's not going away any time soon. It's not about one individual. It's a systemic argument about what the SNP's been doing and therefore Humza has really, and he has to do this pretty quickly, has to set out a new agenda to stamp his mark on being First Minister as opposed to be seen as Nicola Sturgeon's candidate , Nicola Sturgeon's successor."

Ms Sturgeon was arrested on Sunday and questioned for seven hours by officers investigating SNP finances. She was released without charge pending further inquiries and later released a statement to say she was "innocent of any wrongdoing."

The investigation was launched by Police Scotland after it received multiple complaints over the use of more than £600,000 in donations to the SNP to fight a second independence referendum.

Two SNP MSPs, Michelle Thomson and Ash Regan, have called for Ms Sturgeon to withdraw her party membership in an attempt to insulate the SNP from the police investigation.

Ms Regan, who was a candidate in the SNP leadership contest, said this week: “As a party and as individuals in positions of leadership, we should always strive to uphold the highest standards of integrity and accountability.”

Ms Thomson was one of a series of MPs and MSPs stripped of the SNP whip during Sturgeon’s time in charge, which has prompted growing calls for her to be treated in the same manner.

Mr Salmond said yesterday he believed the the SNP is facing an “extinction event” in the wake of Ms Sturgeon’s arrest.

He said his former party’s reputation has been damaged to the extent that the “narrative is now that the SNP find it difficult to run a tap in the Scottish parliament”.

Relations between Mr Salmond and Ms Sturgeon were poisoned when her government investigated complaints of sexual harassment against him five years after he left office.

The investigation was found to have been “unlawful”, “unfair” and “tainted by apparent bias” in a civil case brought by Salmond, and, after he was charged with sexual assaults on nine younger women civil servants and party workers, he was cleared of all charges in a High Court case.

Ms Sturgeon's arrest follows the arrest and subsequent release of both her husband, the former SNP chief executive Peter Murrell, and Colin Beattie, the party’s former treasurer in April.

READ MORE: ‘I’m innocent’: Sturgeon released after arrest over SNP finances probe

Speaking on the Holyrood Sounds podcast, Mr Salmond said the SNP was struggling to regain its footing. “The SNP as a political party is facing a potential — I was going to say — extinction event, maybe that’s a bit alarming, but if you don’t change course, then that’s where it’s heading,” he said.

“Momentum works two ways. It can work in your favour, very substantially. Reverse momentum is equally compelling. And they have to shift the narrative. The narrative now is that the SNP find it difficult to run a tap in the Scottish parliament, is that embarked on confrontational issues with the Scottish population, which are causing significant damage to these groups in society, but more so to the SNP’s reputation, there is a real underlying feeling that key public services are not being run as they should be run.”

However, Sir John Curtice, professor of politics at Strathclyde University, has pointed out that average support for the SNP has remained at 38 per cent since Mr Murrell and Mr Beattie were arrested in April, suggesting that the controversy had failed to dent SNP election hopes.