Senior anti-Brexit politicians could try to drag the Queen into politics by telling her to sack Boris Johnson if he refuses to resign after losing a no-confidence vote.

Anti-Brexit Conservative Dominic Grieve says the Queen should tell the prime minister to resign should he try and ignore a vote in the House of Commons.

MPs opposed to a no-deal Brexit are considering a plan to vote against Johnson in a no-confidence vote this autumn, a move designed to collapse his government and prevent a no-deal Brexit.

Johnson will reportedly simply refuse to resign in this scenario, allow the UK to crash out of the EU, and then call a general election, setting up an unprecedented constitutional crisis.

The Brexit crisis has taken another bizarre turn as senior anti-Brexit politicians discuss dragging the Queen into politics by telling her to sack Boris Johnson if he refuses to resign after losing a no-confidence vote.

Dominic Grieve, the Conservative MP and former attorney general, warned on Tuesday that he would expect the Queen to tell the prime minister to resign should he try and ignore a vote in the House of Commons.

"The constitutional principles are absolutely clear," he told the Times.

"If the Commons is indicating that an alternative government exists which would enjoy its confidence, this can't be ignored.

"The Queen is not a decorative extra. It's true she has sought to keep herself well away from the cut and thrust of politics but at the end of the day there are residual powers and responsibilities which lie with her. She might have to dispense with his services herself."

Dominic Grieve Getty

The warning comes as opposition MPs and a handful of Conservatives consider a plan to vote against Johnson in a no-confidence vote this autumn, a move designed to collapse his government and prevent a no-deal Brexit.

One mechanism being considered is a so-called Humble Address, an archaic parliamentary mechanism which would involve parliament asking the Queen to write to Johnson and removing him from office.

One unnamed MP told the Telegraph: "She would have to sack him. Of course she would."

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Many MPs determined to stop a no-deal Brexit believe that a confidence vote that triggers a general election is now the last mechanism available to prevent the UK from crashing out of the EU with no deal.

But Dominic Cummings, the most senior aide in Downing Street, has reportedly warned that Johnson will simply refuse to resign during the 14-day period following a vote of no-confidence, allow the UK to crash out of the EU, and then call a general election.

Speaking to Sky News on Wednesday morning, Cummings said: "The most simple thing is the PM believes that politicians don't get to choose which votes they respect. That's the critical issue."

Addressing Grieve's remarks, he said: "Mr Grieve will see what he's right about."

Would the Queen really sack Boris Johnson?

Queen Elizabeth II WPA Pool/Getty

Under this potential plan, MPs would vote to topple Johnson's government, force the prime minister to resign, and use an allotted 14-day period to try and find a majority for an alternative government, comprised of opposition MPs as well as a small number of Conservatives.

The government would form expressly for the purpose of delaying Brexit by seeking an extension to Article 50,before calling a general election.

The plan is fraught with potential loopholes.

Constitutional expert Catherine Haddon said this week that Johnson would not legally be obliged to resign immediately after losing a confidence vote.

"In terms of a strict reading of the legislation, Boris is not required to resign. It is completely silent on all of this," she told the Times. "The onus is on the incumbent prime minister — they get to choose whether they resign. If they do not it is hard for a new government to be formed without dragging the Queen into politics.”

There is also very little historical precedent for the ruling monarch to take a hands-on role to try and usurp a resistant prime minister.

Royal historian Robert Lacey told Politico: "The queen has a horror of being dragged into politics, partly because it is in her very nature to be neutral and retiring, and also because she deeply believes that the constitutional monarchy should do all it can to remain above the fray."

He said it was "unlikely" that the Queen was likely to get involved.