The Scotsman can reveal Crown Office officials refused to release evidence of discussions between the Crown Office and Police Scotland around the investigation into the SNP.
Crown Office officials claimed the information should not be released as it was not in the public interest in response to a Freedom of Information request for correspondence.
The SNP is under investigation for allegedly misusing more than £600,000 of crowd-funded donations given to the party as part of a fundraising drive, ostensibly to fund a future referendum campaign.
The party denies it has acted improperly and has labelled the allegations part of a “dirty tricks” campaign by opponents within the independence movement.
Restricted funds are not separated out within the SNP or any other major party’s accounts. However, the SNP came under pressure after activists demanded sight of where the “ringfenced” funds were in the accounts.
Months of bitter internal infighting followed, which included the-then former treasurer, Douglas Chapman MP, and high-profile MP Joanna Cherry stepping down from their positions on the party’s national executive committee earlier this year due to concerns around transparency.
In response to the concerns the newly appointed treasurer, Colin Beattie, claimed the sum raised was “earmarked” to be spent in the future, adding that “amounts equivalent” to the money raised would be spent on campaigning for a second referendum.
Following an initial assessment period, Police Scotland announced on July 13 that it had opened a full, formal investigation into the allegations of fraud and financial irregularlity. In July, The Times reported accusations the Crown Office had attempted to change the wording around the investigation into the SNP.
According to one source cited by the paper, the prosecution service had lobbied for a change in the wording to be closer to a “fact-finding” exercise rather than a formal investigation, raising concerns there was interference in the process by the Crown.
However, any correspondence between the two is to be kept secret after the Crown Office claimed it would not be in the public interest to release the information.
One official at the Crown Office said in response to the request that disclosure of the discussions would “inhibit the future provision of free and frank advice” by those working for the Crown Office.
They also claimed it would “not be in the public interest” to disclose advice provided by the Crown to Police Scotland in relation to an ongoing investigation.
The official said: “I consider that if the information was released, this would inhibit the future provision of free and frank advice without reserve and inhibit the free and frank exchange of view for the purposes of deliberation.
"Further, it would not be in the public interest to disclose prosecution service advice to Police Scotland while a police investigation is ongoing.”
The response is now subject to an internal review within the Crown Office.
A spokesperson for the Crown Office and Procurator Fiscal Service (COPFS) said: “There has been no disagreement between COPFS and Police Scotland about how this investigation should be progressed.
“It would not be in the public interest to disclose prosecution service advice to Police Scotland while an investigation is ongoing.”
Police Scotland and the SNP were contacted for comment.