Mr Beattie, who has been the party's treasurer for a number of years, was detained by police investigating the party's funding and finances earlier on Tuesday.

The news came shortly before First Minister Humza Yousaf was due to make his first major statement in Holyrood, setting out his priorities in office.

Speaking in parliament, the new SNP leader said being first minister was "not without its challenges" - to laughter from fellow MSPs - but he insisted he was focused on the "genuinely difficult challenges" facing Scotland.

However, Scottish Labour leader Anas Sawar branded Mr Yousaf a "lame duck" first minister, leading a party engulfed in scandal".

"In three short weeks, we already have a lame duck first minister and a lame duck government," he said, adding that Scotland needed a "new energy" that Mr Yousaf could not provide.

'Highly significant next step' as Colin Beattie arrested in SNP finance probe - politics latest

Mr Yousaf - who attempted to offer a "fresh start" in his speech in Holyrood - admitted to Sky News that Mr Beattie's arrest was "not helpful".

Asked whether he was "surprised" at the news of Mr Beattie's arrest, he said: "Of course I'm surprised when one of my colleagues is arrested," he said.

Despite the development, Mr Beattie has not been suspended from the SNP, Mr Yousaf told reporters earlier.

"I've said already that people are innocent until they are proven guilty," he added.

Explainer - Why have senior SNP executives been arrested and what are police investigating?

Police Scotland did not name the arrested man but said a 71-year-old suspect was detained on Tuesday.

"The man is in custody and is being questioned by Police Scotland detectives," the force said.

"A report will be sent to the Crown Office and Procurator Fiscal Service."

It added: "As the investigation is ongoing we are unable to comment further."

Mr Beattie is the second arrest of a high-profile SNP figure in just a matter of weeks.

Peter Murrell, the SNP's former chief executive and Nicola Sturgeon's husband, was detained by police earlier this month in connection with the investigation into the party's finances.

He was later released without charge pending further investigations after an 11-hour detention.

At the same time that he was in police custody, detectives seized a £100,000 motorhome from outside the home of one of Mr Murrell's elderly relatives.

In another move that has hit the party, it emerged days after Mr Murrell's arrest, its long-standing auditors Johnston Carmichael quit.

There have been questions hanging over Mr Yousaf after he admitted that the party's auditors had in fact quit months before the official announcement and he had not been aware at the time.

Asked whether it was wrong of Ms Sturgeon not to reveal to SNP leadership candidates the lack of auditors, Mr Yousaf said: "Frankly it would have been helpful to know beforehand.

"I think people have a reasonable question to ask the party around transparency. I have committed to a review of governance with external input."

Mr Yousaf also said he was unaware the SNP owned the motorhome until he became party leader in recent weeks.

The new SNP leader - who billed himself as the "continuity candidate" during the race to replace Ms Sturgeon - is under pressure to distance himself from his predecessor following the series of damaging events which have overshadowed his first few weeks in the top job.

Over the weekend, a video emerged in which Ms Sturgeon appeared to tell the party's ruling body back in March 2021 to "be very careful" about suggesting the SNP was suffering from financial problems.

There were reports that Mr Beattie had issued a stark message about the SNP's cash flow, warning that it was difficult to balance the books.

Mr Yousaf has faced calls to suspend Ms Sturgeon from the party if she failed to resign herself.

He will address the Scottish Parliament today for the first time since the Easter recess, in a session that reports suggest Ms Sturgeon will be absent for.

On Monday, the party's former leader in Westminster, Ian Blackford, sought to defend Ms Sturgeon and dismissed rumours that she could quit the party.

The Daily Telegraph quoted a source within the party saying she planned to step down "sooner rather than later" amid the ongoing controversies - but Mr Blackford rejected this as "idle speculation", telling the BBC she still had "an awful lot to give".