A senior figure in the Scottish National party has said the party faces its biggest crisis in 50 years, amid a police investigation into its finances. Mike Russell, the SNP’s president and a former minister, also said he did not think independence could be achieved “right now”. On Wednesday, the party’s former chief executive Peter Murrell was arrested by police investigating the spending of about £600,000 that was earmarked for an independence campaign. Murrell, the husband of the party’s former leader Nicola Sturgeon, was released on Wednesday evening without charge pending further investigation. Police searched the couple’s home in Glasgow for more than a day, and uniformed officers also searched the SNP’s headquarters in Edinburgh. In an interview with the Herald newspaper, Russell said recent weeks had been “wearing” for the SNP, which recently selected Humza Yousaf to succeed Sturgeon as party leader. He said: “In my 50-year association with the party, this is the biggest and most challenging crisis we’ve ever faced, certainly while we’ve been in government. But I have an obligation to this party and the movement for Scottish independence that’s been such a massive part of my life for so long.” He continued: “I don’t think independence can be secured right now; we need to work towards some coordinated campaigning. But I think this is achievable. My main focus is how we can create a new Yes movement that allows for different visions but conducted in an atmosphere of mutual trust.” Russell said there would be a wide-ranging review of the SNP’s governance and transparency. This was promised by Yousaf, who was sworn in as first minister last week. On Friday, it emerged that the accountancy firm that audits the SNP’s finances had resigned, after working with the party for a decade. The accountants Johnston Carmichael informed the party of the decision before Murrell’s arrest. The party’s treasurer is now seeking another auditor in order to comply with Electoral Commission rules.