The accounting firm which audited the SNP's finances has resigned amid an on-going police investigation.
The party was rocked this week when the Glasgow home shared by its former chief executive and Nicola Sturgeon was searched by officers for two days.
Murrell was arrested on Wednesday morning and questioned for several hours before being released without charge.
The SNP head office in Edinburgh was also searched on Wednesday.
Police Scotland has led a long-running investigation into SNP finances after several complaints were made in 2021 regarding a fundraising drive for independence campaigning.
Accountancy firm Johnston Carmichael has now ended its decade-long business relationship with the party after reviewing its client portfolio.
BBC Scotland reported the decision was made before Murrell was arrested this week.
An SNP spokesman said: “We can confirm that Johnston Carmichael will not be providing audit services to the SNP this year. The national treasurer is undertaking a tendering process for alternative provision and we have advised the Electoral Commission of that position.”
A spokesman for Johnston Carmichael said: “As a regulated organisation, we adhere to our obligations on client confidentiality and do not discuss client business.”
The SNP is required to prepare financial statements in accordance with the Political Parties, Elections and Referendum Act 2000.
But Electoral Commission rules state any party with income or expenditure of more than £250,000 is required by law to also independently audit their accounts and include this report in their submission.
Accounts are from the calendar year, not the financial year and the deadline for 2022 accounts is July 7. If there is no report and no reasonable excuse, the commission has the power to appoint its own firm of auditors to look at the accounts.
The SNP's accounts for 2021 were published on 16 August 2022. The party's total income was £4,510,460, total expenditure was £5,262,032, assets were £1,630,454 and liabilities were £1,055,689.
First Minister Humza Yousaf said his party had "fully co-operated" with police and would continue to do so. He said that he was "very, very clear that the governance of the party was not as it should be".
Scottish Labour deputy leader Jackie Baillie said the resignation of Johnstone Carmichael was a deeply worrying development that posed "serious questions" about the SNP's financial affairs.
She said: "Yesterday, Humza Yousaf attempted to distance himself from the legacy of Peter Murrell - today we need to know what the current first minister plans to do to get the SNP's house in order. Sunlight is the best disinfectant - we need transparency and openness from the SNP now."
Scottish Conservative constitution spokesperson Donald Cameron said the SNP should be "fully transparent" over why their auditors decided to quit.
To sign up to the Daily Record Politics newsletter, click here.
