Colin Beattie, who was in the role for a total of nearly 20 years, was asked by journalists whether he knew about and had signed off the purchase.

"No, I didn't know about that," he said.

He later said although he did not know about the transaction at the time of purchase, he found out about it in the 2021 annual accounts.

Mr Beattie quit as treasurer the day after he was arrested by police as part of an ongoing investigation into the party's finances.

He was subsequently released without charge pending further investigation.

The Niesmann and Bischoff vehicle, which can retail for more than £100,000, was seized by police from outside the home of former SNP chief executive Peter Murrell's mother in Dunfermline.

The motorhome was removed on 5 April - the same morning that Mr Murrell became the first senior party figure to be arrested in the probe.

He was later released without charge.

Officers spent two days searching the couple's home in Glasgow. The SNP's headquarters in Edinburgh were also searched.

Ms Sturgeon, who is married to Mr Murrell, said on Tuesday that the crisis that has engulfed the SNP in recent weeks was her "worst nightmare".

She insisted that the police investigation did not influence her decision to stand down as first minister in February.

She said she "could not have anticipated" what happened in the weeks since she resigned and only knew that her husband was to be arrested when officers arrived on their doorstep.

Ms Sturgeon also said she had not been spoken to by police, and intended to stay on as MSP for Glasgow Southside.

But she refused to speak about the motorhome, which is reported to have sat on the driveway of her mother-in-law's house since January 2021.

Mr Beattie was not SNP treasurer at the time, having lost an internal vote to Douglas Chapman the previous November after 16 years in the role.

He was reappointed when Mr Chapman quit in May 2021 after saying he had "not received the support or financial information" that was needed to carry out his duties as treasurer.

The Daily Record said it had been told by party sources that the motorhome was bought as a potential "battle bus" ahead of the last Scottish Parliament election in May of that year but was never used.

The party had generally hired vehicles to use during previous election campaigns.

Humza Yousaf, who succeeded Ms Sturgeon as SNP leader and first minister last month, has previously said he only learned about the motorhome after he won the leadership contest and saw a police warrant that gave details of items officers wanted to confiscate.

The SNP's Westminster leader Stephen Flynn was later asked about the motorhome as he spoke at an Institute for Government event in London, and said he only became aware of the purchase "when it was printed on the front of a newspaper".

The seized motorhome was spotted in a police compound in Govan last week

Scottish Conservative chairman Craig Hoy said Mr Beattie's admission that he did not know about the motorhome "beggars belief" and left "serious questions to answer".

He added: "Humza Yousaf should have long since suspended senior SNP figures like Peter Murrell, Nicola Sturgeon and Colin Beattie while this investigation is ongoing, but he has failed to show any signs of leadership".

Scottish Labour deputy leader Jackie Baillie said the revelation "lays bare the chaos at the heart of the SNP", adding: "That the treasurer of the party did not know that over £100,000 had been spent on a motorhome is mind-boggling."

The leader of the SNP's Westminster group, Stephen Flynn, said on Monday that it could miss out on £1.2m in public funds if it fails to file its accounts by the 31 May deadline.

The party is having problems finding new auditors after the previous company resigned in September - although Mr Yousaf has said he did not find out the firm had quit until after he became party leader.

Senior figures in the Westminster group are said to be at loggerheads after former leader Ian Blackford accused his successor Mr Flynn of giving him false assurances about the group's auditors.

Mr Blackford told the BBC he had been told by Mr Flynn in a phone call on 7 April that the group had an auditor in place, but a senior SNP source disputed his version of events.

'No assurances'

The source said a discussion had taken place "but no assurances were provided that this would be certain and would meet deadlines".

The BBC is unable to verify which account is accurate.

The Westminster group has still not found an auditor and senior figures have admitted that meeting the 31 May deadline will be "challenging".

The SNP as a whole has also not yet appointed a new auditor despite having to file its accounts with the Electoral Commission by 7 July.

A spokeswoman for the commission said on Tuesday: "The SNP informed us by telephone in early February this year that their auditors had resigned. They also asked what the process would be if they needed to ask for an extension for submitting their accounts."

Mr Yousaf is due to speak with SNP MPs on Tuesday afternoon as part of a visit to London that saw the new first minister meet Prime Minister Rishi Sunak the previous evening.

Police Scotland launched its Operation Branchform investigation in July 2021 after receiving complaints about how more than £600,000 of donations raised by activists for a future independence referendum campaign were spent.

Questions were raised after accounts showed the SNP had just under £97,000 in the bank at the end of 2019, and total net assets of about £272,000.

Last year it emerged that Peter Murrell gave a loan of more than £100,000 to the SNP to help it out with a "cash flow" issue after the last election.

The party had repaid about half of the loan by November of that year, but Mr Yousaf admitted last week that the party still owed money to Mr Murrell.