The Scottish Conservatives said scandals were continuing to “engulf” the party and called on Humza Yousaf to tackle the situation “head-on”.

Mr Yousaf, the new First Minister, told journalists he did not believe the SNP is being run in a criminal way. He said Colin Beattie, the treasurer, would not be suspended from the party after it emerged the 71-year-old had been taken into custody and was being questioned by detectives.

However, he said there are “pertinent issues” over Mr Beattie’s role as treasurer, and over his membership of the Scottish Parliament’s public audit committee.

The arrest of Mr Beattie, who also serves as an MSP for Midlothian North and Musselburgh, is the second related to the investigation into how more than £600,000 in donations to the party earmarked for an independence referendum were used.

Earlier this month, former party chief executive Peter Murrell – who is also Nicola Sturgeon’s husband – was arrested and questioned for more than 11 hours before being released without charge “pending further investigation”.

It came as Mr Yousaf announced he would delay or rethink a number of policies advanced by his predecessor, Ms Sturgeon. Setting out his priorities in Holyrood, he said plans to introduce a deposit return scheme for drinks cans and bottles would be delayed until March next year, and also promised to “go back to the drawing board” on controversial proposals to introduce further restrictions on alcohol advertising.

Mr Yousaf had hoped the announcements would form part of a “reset”. However, his speech was overshadowed by Mr Beattie’s arrest, with the First Minister forced to deal with more than one media scrum in the Scottish Parliament.

Asked if Mr Beattie had been suspended from the party, he told journalists: “I’ve said already that people are innocent until proven guilty.”

Mr Yousaf said it was a “really important point of natural law, really, that people are presumed innocent until found guilty”, adding: "And, of course, if they are guilty then I would take the appropriate action – whether that is suspension, or indeed going even further than that. But it's really important that due process takes place."

Asked if this meant no one will be suspended unless they are found guilty, he added: "If there are charges, I would be happy to look at the circumstances at that point. We may well have to take that course of action. But again, we are getting ahead of ourselves. There has been questioning under caution, which is not insignificant, but of course no charges – as far as I'm aware – have been brought forward as we speak."

Asked if Mr Beattie would be removed from the public audit committee, Mr Yousaf said he would “consider” this, adding: “I’ll have to speak to Colin. My understanding is he’s still in the police station being questioned.” He added: “Clearly there are pertinent issues around his role on the public audit committee and his role, of course, as the national treasurer.”

Mr Yousaf said he was surprised by Mr Beattie’s arrest. "Of course I’m surprised that one of my colleagues has been arrested,” he told journalists. He said the timing was “far from ideal”.

Asked if he could guarantee the SNP is not operating in a criminal way under his leadership, Mr Yousaf said: “Certainly, I don’t believe it is at all, no. I’ve, as you know, instructed a review into transparency and good governance, and of course with the issue around financial oversight, and I want some external input into that. There is change that is needed within the way the party has operated, I’ve made that absolutely clear.”

Earlier, a spokesperson for the SNP said: “We have no comment on a live police investigation.”

Mr Beattie was the SNP’s national treasurer between 2004 and 2020, losing the position to MP Douglas Chapman. However, Mr Chapman quit the post in 2021, claiming he was not being given the required information to carry out the job, and Mr Beattie took on the role again.

He reportedly told the party’s ruling body on Saturday the SNP would struggle to balance the books.

There was no sign of police activity outside Mr Beattie’s address in Dalkeith, Midlothian, on Tuesday morning, or outside his constituency office in the town.

Meghan Gallacher, deputy leader of the Scottish Conservatives, said the SNP is in “total meltdown”. Her party called for Mr Beattie, Mr Murrell and Ms Sturgeon to be suspended from the SNP.

She said: "It is past time that Humza Yousaf tackled this scandal head-on and proved to the Scottish public that he is his own man, instead of defending and deflecting from his predecessor’s tarnished legacy.”

Labour leader Sir Keir Starmer said the SNP is in a “real mess”. During a visit to York University, he was asked about the arrest of Mr Beattie.

Sir Keir told broadcasters: “The SNP developments are deeply concerning. Obviously there is a criminal investigation going on, so there is only so much I can say. But after 16 years in power, it has descended to this – a real mess – and those being let down are Scottish voters, who are entitled to better than this.”

Scottish Labour deputy leader Jackie Baillie said: “This is yet another deeply concerning development and the Police Scotland investigation must be allowed to proceed without interference.”

A Police Scotland statement said: “A 71-year-old man has today, Tuesday, 18 April 2023, been arrested as a suspect in connection with the ongoing investigation into the funding and finances of the Scottish National Party.

“The man is in custody and is being questioned by Police Scotland detectives. A report will be sent to the Crown Office and Procurator Fiscal Service.

“The matter is active for the purposes of the Contempt of Court Act 1981 and the public are therefore advised to exercise caution if discussing it on social media. As the investigation is ongoing we are unable to comment further.”

Analysis: Humza Yousaf's big day 'torpedoed' by arrest of SNP treasurer

SNP facing claims it is in ‘total meltdown’ after arrest of party treasurer