In a statement released on Wednesday, Police Scotland confirmed Mr Murrell, 58, had been arrested in connection with its investigation into the alleged ‘missing £600,000’ within the SNP’s finances.

Mr Murrell was later released without charge “pending further investigation”, Police Scotland said in a statement.

Ms Sturgeon would “fully co-operate if required” with police as part of an investigation into the SNP’s finances, her spokesperson said last night.

The spokesperson said: “It would not be appropriate to comment on a live police investigation. Nicola Sturgeon had no prior knowledge of Police Scotland’s action or intentions.

“Ms Sturgeon will fully co-operate with Police Scotland if required. However, at this time no such request has been made.”

Heavy police presences could be seen outside the home shared by Mr Murrell and Ms Sturgeon in Glasgow, as well as outside the SNP’s Edinburgh headquarters, a stone’s throw away from the Scottish Parliament.

Dozens of officers, in unmarked and marked cars, made their way into the headquarters during the morning.

Former SNP chief executive Peter Murrell, the husband of Nicola Sturgeon, is understood to have been arrested by Police Scotland over an investigation into the party’s finances.

Officers have been investigating the SNP’s finances for more than a year after complaints were made in July 2021 about alleged misuse of party donations to a fund for independence campaigning.

The statement said: “A 58-year-old man has today, Wednesday, April 5, 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.

"Officers are also carrying out searches at a number of addresses as part of the investigation.

A 58-year-old man has been arrested in connection with the police investigation into the SNP's finances.

"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.”

A spokesperson for the Crown Office and Procurator Fiscal Service said: “COPFS will continue to work with police in this ongoing investigation.

“It is standard practice that any case regarding politicians is dealt with by prosecutors without the involvement of the Law Officers.”

Mr Murrell resigned as chief executive of the SNP just weeks ago following a row over membership numbers which also saw the resignation of the party’s head of communications and media. It had been a role he had held since 1999, around 24 years.

It also emerged Mr Murrell had loaned more than £100,000 to the party during June 2021, with the SNP repaying half of that money by October of the same year.

It was around this time the then party treasurer, MP Douglas Chapman, resigned citing a lack of information on the party’s finances.

Ms Sturgeon has also denied her resignation as First Minister had anything to do with the ongoing investigation into the party’s finances.

Her successor, Humza Yousaf, said the arrest of Mr Murrell was “not great” for trust in the party as he stressed he has had “no involvement” in the party finances.

The new First Minister, who is just over a week into his job, said he could not comment on a live police investigation, but that his party was “fully co-operating”.

He told reporters during a visit to New Gorbals Health and Care Centre in Glasgow, “as you’ll understand, I can’t comment on a live police investigation but what I can say and what reassurance I absolutely can give is that the SNP has been fully cooperating in that police investigation and will continue to do so.

"The party agreed at my first NEC as party leader that we’d instruct a review into governance and transparency of the party with some external input.”

He added he was made aware of the arrest of Mr Murrell “this morning, after the event, and I think that’s really important for me to stress”.

Mr Yousaf said: “I am following it just as much as anybody else is but as I keep saying the party will fully cooperate as has already been reported, for example, that police are at party headquarters and they will not be impeded in any way shape or form in terms of their investigation.”

He added: “The sooner we can get to a conclusion in this police investigation the better but it is really up to the police to of course investigate in due course in the way that they see fit and appropriate.

"We’ll make sure that we fully cooperate and what I can do as the new SNP leader, somebody who has no involvement in the party finances in the past, is hopefully bring new leadership and I think the review that I’ve spoken about and the NEC has agreed into governance and transparency with that external input is going to be key.”

SNP figures told The Scotsman the decision to arrest Mr Murrell had shocked the party.

Government ministers appeared to get no warning of the imminent arrest, with some finding out via family members who had been watching the news.

A spokesperson for the SNP said it would not be appropriate to comment.

They said: “Clearly it would not be appropriate to comment on any live police investigation but the SNP have been cooperating fully with this investigation and will continue to do so.

“At its meeting on Saturday, the governing body of the SNP, the NEC, agreed to a review of governance and transparency – that will be taken forward in the coming weeks.”

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

Donald Cameron, the Scottish Conservative spokesperson for the constitution, said: “Senior SNP politicians, including Nicola Sturgeon and Humza Yousaf, must cooperate fully with the investigation into this very serious case and commit to openness and transparency.

“While there is an ongoing police investigation into the SNP’s finances, and given that a suspect has now been arrested, it is right that due process is followed and any potential wrongdoing investigated thoroughly by the police.”

Peter Murrell arrested: Former SNP chief executive and Nicola Sturgeon's husband arrested in connection with SNP 'missing £600k' investigation