Alex Salmond is suing the Scottish Government after he was reported to police over a historic allegation dating back to his time as First Minister.
The incident is alleged to have occurred in the First Minister’s official residence of Bute House in December 2013.
Mr Salmond accused the Permanent Secretary to the Scottish Government of “behaving unlawfully” in its application of the complaints procedure and said he will take his case to the Court of Session.
And in a move that could plunge the SNP into civil war, he said “the administration at the senior levels of the Scottish Government will have the most serious questions to answer” if the Court of Session finds in his favour.
A Scottish Government spokeswoman said: “For legal reasons, we are currently unable to comment.”
A Police Scotland spokesman said: “Police Scotland is not going to comment on whether an inquiry is ongoing.”