The inquiry, known as Operation Branchform, into the spending of more than £600,000 in party donations earmarked for independence campaigning has been under way since July 2021.
It was launched after a number of complaints were made to Police Scotland when the money did not appear to be in the party’s accounts.
In 2023 former First Minister Nicola Sturgeon, and former SNP treasurer Colin Beattie, were both arrested and released without charge relating to the inquiry.
Peter Murrell, who has separated from Ms Sturgeon pending their divorce and is the former SNP chie executive, was charged last year in relation to alleged embezzlement of party funds.
The couple’s home and the SNP’s headquarters were both searched by officers in April 2023.
Questions have been raised as to the length of the investigation, with Lord Carloway, Scotland’s most senior judge, claiming in January it appeared there was a “hold-up” with the criminal investigation.
It has since emerged that Police Scotland has spent over £2.1 million on the investigation as of the end of January — an increase of around £800,000 in the past year.
A freedom of information request, first reported by the Scottish Daily Mail, revealed the total policing costs of £2,106,961 “does not include pension contributions” of officers working on the case.
Previous reports showed £1.3 million had been spent between 2021 and the start of 2024, meaning an expenditure of about about £800,000 on the inquiry in the past year.
Craig Hoy, the Scottish Conservative finance spokesman, said: “The ever-increasing costs of this probe into the SNP’s murky finances reflects the seriousness of the situation.
“With sustained SNP cuts biting across the justice system, this will be having a huge impact on the resources available to the force.”
Police submitted an “advice and guidance report” to prosecutors detailing their findings and seeking formal advice on how to proceed last year. The Crown Office said the report was under consideration and investigations into Ms Sturgeon and Mr Beattie continue.
A separate bill for prosecutors sits at about £200,000.
Police Scotland said: “On August 9 we presented the findings of the investigation to the Crown Office. We await their direction on what further action should be taken.”
A Crown Office spokesman said: “A prosecution report has been received in relation to a 60-year-old man. Connected investigations of two other individuals, a man aged 73 and a 54-year old woman, remain ongoing.
“Prosecutors will review this report and make decisions on the next steps. Prosecutors operate independently of political influence.”
