The United Kingdom’s former Attorney General has said the Prime Minister must resign if he has misled The Queen over prorogation.

Speaking to BBC News, Dominic Grieve QC said: “If Boris Johnson has misdirected Her Majesty the Queen, it would be a shameful act and he must resign immediately.”

Mr Grieve’s intervention comes after three of the highest judges in the land ruled that the Prime Minister has misled The Queen over proroging Parliament.

The Scottish Court in Session ruled that the advice conveyed was unlawful because “It had the purpose of stymying Parliament.”

The government will appeal the decision to the Supreme Court.

Dominic Grieve QC says the Prime Minister should resign if he has misled The Queen (photo: Chris McAndrew / UK Parliament)

Lawyers acting for the winning party at court believe that the ruling means Parliament is now back in session, with Parliament no longer being prorogued.

However, it is understood that for the time being, Parliament will only be recalled if the government loses their appeal at the Supreme Court next Tuesday.

The official summary of the ruling said: “The Court will accordingly make an Order declaring that the Prime Minister’s advice to HM the Queen and the prorogation which followed thereon was unlawful and is thus null and of no effect.”

The Government said it is “disappointed” by the decision saying that prorogation was ” legal and necessary.”

Questions are already being raised over whether the monarch can trust 10 Downing Street to give her lawful advice.

Dr Catherine Haddon, a Senior Fellow at the Institute for Government, said: “Regardless of the final outcome, it is pretty uncomfortable position for the Palace.

“HM acts on the Advice of her PM. For a court to rule that advice was unlawful, even if the ruling is later rejected, opens up questions about how that advice is given. She has to be able to trust No.10.”