Alex Salmond has said that Gordon Brown’s meeting with the Duke and Duchess of Cambridge shows a “unionist desperation” over the constitution.
It comes after the former prime minister met with William and Kate privately at the Palace of Holyroodhouse last week.
Alba party leader Salmond indicated that it would be “foolish” to have a situation where the monarchy is seen to be involved in the debate over whether Scotland should be independent or not.
In a video message to his party’s supporters, the former First Minister of Scotland said: “Whatever Prince William thought he was doing by agreeing to a confab with Gordon Brown just as he set up his latest campaign for the union… we should have no hesitation in seeing from that meeting, unionist preparation for attempting to persuade a constitutional monarchy to intervene in a constitutional debate which should be left to the people.
“It would be very wise for the Royal Family to follow what has been the Queen’s example over her long reign, to keep the monarchy over and above politics, and it would be foolish to have a situation in which it can be said that the monarchy is involved in the Scottish constitutional debate.
“Back in 2014 David Cameron made a last ditch desperate and failed attempt to drag the Queen into politics. The Brown meeting shows poor judgement on both sides but the same degree of unscrupulous unionist desperation. The independence team should take note.”
He continued: “It is quite clear that the forces of the union, David Cameron previously, and now Gordon Brown, have no compunction in getting themselves ready and set for what is coming in the next referendum campaign.
“However, the Scottish Parliament elections have left them in a state of disarray. That is why the case for Scottish independence must be progressed now as a matter of urgency.”
Salmond also urged supporters of independence to “strike when the iron is hot” on progressing their cause following the Holyrood election.
He added: “The Tories at Westminster are surprised that they are not already facing a renewed constitutional challenge and are wondering what on earth is going on.
“It would be infinitely better for the independence side to seize the moment and strike when the iron is hot to progress the constitutional issue.
“Alba’s membership continues to rise as we press for the case for Scottish independence to be progressed with urgency and democratic determination. “