In a statement issued this morning, Police Scotland said: “The man is in custody and is being questioned by Police Scotland detectives. A report will be sent to the Crown Office and Procurator Fiscal Service.”

The force added: “The matter is active for the purposes of the Contempt of Court Act 1981 and the public are therefore advised to exercise caution if discussing it on social media.

“As the investigation is ongoing we are unable to comment further.”

Mr Beattie’s arrest comes two weeks after former SNP chief executive Peter Murrell, the husband of former First Minister Nicola Sturgeon, was arrested as part of the same probe and subsequently released without charge.

Police Scotland launched the ‘Operation Branchform’ investigation into the SNP’s finances in 2021 after allegations were made that the party had wrongly spent funds which it said were “ring-fenced” for a future independence referendum campaign.