A former SNP activist whose complaint to Police Scotland helped spark a long running investigation into party finances has called for chief constable Jo Farrell to give a public update on the probe.

The independence supporter donated sums of money through a Scot Ref website in 2017/18 for a second referendum to be held.

However, in the absence of indyref2 he made a complaint to the force in August 2020.

He spoke out as The Herald was told by the Crown Office that it had yet to receive a report from Police Scotland on Operation Branchform.

READ MORE: Operation Branchform: Police chief rejects attacks on SNP probe

"I would like to see the chief constable give the public an interim report telling us where the are with the investigation and what they have discovered so far," the former SNP activist told The Herald.

"If it is indeed that they have uncovered other things and need more time then that is fine. But it would be good to know why it is taking so long. You would think anyone who can read accounts could get to the bottom of it.

"Some people who donated money have now passed away. They will never know what happened. It needs to be resolved as quickly as possible."

The Herald: Officers from Police Scotland searched the home of Nicola Sturgeon and Peter Murrell. Photo: PA.

Police Scotland opened the formal investigation Operation Branchform into SNP finances in the summer of 2021 over concerns about a ring-fenced independence referendum campaign fund.

The force later said that its inquiry was looking at alleged fraud. It has arrested, questioned and released without charge the SNP’s former chief executive, Peter Murrell, his wife and the former party leader and first minister Nicola Sturgeon, and the former party treasurer Colin Beattie.

Police are understood to have taken an interest in a camper van and a Jaguar SUV. Forensic officers searched Mr Murrell and Ms Sturgeon’s Glasgow home and the party’s Edinburgh HQ in April last year.

READ MORE: SNP MSP says police manpower being misused in probe into his party

SNP insiders have been frustrated by how long the investigation has been taking.

The police probe stepped up just weeks after Humza Yousaf succeeded Ms Sturgeon as SNP leader and First Minister after he won the party's leadership election last year, significantly damaging the beginning of his career in the top roles.

He was also seen to be at a disadvantage as he was regarded as the preferred choice of successor by Ms Sturgeon whose popularity dropped as a result of the investigation. Polls also suggest support for the SNP has decreased as a result of the probe.

READ MORE: Sturgeon defends legacy in first speech to Holyrood since exit as FM

A party source, speaking to the Sunday Mail last month, said: “Things appear to have gone quiet for some time, but the investigation is continuing behind the scenes. Nobody knows when there will be a significant development and that is a problem for the party because we cannot really move on until this is over.

“Internally, senior people are furious that it is not being resolved one way or another and there is a fear that things could suddenly blow up in the middle of a general election campaign, for example. The police have been clear that they will move at their own pace and that they are not going to be rushed or take political factors into consideration.

“But the fact is this is having a huge impact on Scotland’s politics and democracy, even if that is not the police’s intention. There are things Humza Yousaf could do to distance his administration from Nicola Sturgeon’s time as first minister, but he is clearly determined to stand by her, which does not make things easier.”

READ MORE: Yousaf facing SNP backbench rebellion over justice reforms

It emerged last year that Police Scotland had spent £1 million on its investigation into SNP finances, more than the alleged £600,000 which was reported missing.

Senior figures in the SNP have previously criticised the inquiry.

Murray Foote, the SNP's former head of communications in Holyrood, who succeeded Mr Murrell as the party's chief executive, hit out over the force putting up a forensic tent in Ms Sturgeon's and Mr Murrell's front garden.

He also questioned whether it could be a "wild goose chase". Mr Foote made the comments after he had resigned his role as the party's communications chief and before he was appointed chief executive.

A spokesman for the Crown Office and Procurator Fiscal Service said: "The situation remains that COPFS has not received a Standard Prosecution Report in this matter."

A Police Scotland spokesperson said: "As the investigation remains ongoing we are unable to comment further."