Scotland’s top police officer today insisted the probe into the SNP’s finances was “proportionate” and being conducted with “integrity”.
In his first public comments on Operation Branchford, Sir Iain Livingstone also said there must not be any political interference in the investigation.
Sir Iain mentioned the probe into the SNP’s funding and finances at a meeting of the Scottish Police Authority’s board on Thursday.
He said: “Police investigations must be allowed to progress without any form of political interference.”
Police decisions will always be taken in accordance with the rule of law rather than political or constitutional matters, he added.
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Sir Iain said: “Under Operation Branchform, a dedicated team of officers from Police Scotland’s specialist crime division continue their investigation into the funding and finances of the Scottish National Party.
“A diligent, thorough and proportionate criminal inquiry is being conducted with integrity.
“Two individuals have been arrested and subsequently released without charge, pending further investigation, investigations which continue.”
The chief constable said he recognises there is a high level of interest in the case, but he urged against speculation which could undermine the inquiry.
He said the timescales of the probe will be set by investigative considerations rather than political ones.
Sir Iain continued: “I would request, I would urge, all civic leaders – if offering any comment or thoughts on what is a live investigation, to act with prudence and responsibility.
“Wholly inaccurate assertions and uninformed speculation will only serve to damage justice, infringe the rights of individuals and undermine the rule of law.”
Last month, officers swooped on Nicola Sturgeon’s Glasgow home and the SNP’s headquarters in Edinburgh as part of the investigation, which centres on how more than £600,000 in donations to the party earmarked for an independence referendum has been used.
In dramatic scenes, officers erected a blue tent outside the property Ms Sturgeon shares with her husband Paul Murrell, the SNP’s former chief executive.
The probe has seen Mr Murrell and ex-treasurer Colin Beattie arrested and subsequently released without charge pending further investigation.
Ms Sturgeon yesterday described the developments as “unexpected and unwelcome”.
In her first column for the Glasgow Times newspaper since quitting as Scottish First Minister, Ms Sturgeon wrote: “When I decided to step down from the government, I knew that I faced a period of adaptation.
“Being a senior government minister involves almost every minute of every working day being accounted for by meetings, engagements, briefing papers and questions in Parliament.
“To go from 16 years of that to being a backbencher – still an incredibly busy job but without the weight of government responsibility – was always going to be a difficult transition.
“And, of course, since I stepped down, there have been unexpected and unwelcome developments that I am not able to expand upon here, but which have made this period even more challenging.
“However, in spite of that, I am enjoying the new perspective and different focus that comes with no longer being First Minister.”