British Prime Minister Theresa May’s cabinet allies have been forced to fend off reports that there’s a plot to oust her as leader, as the country braces for a critical week that’s expected to see her Brexit plan blocked from a third vote in parliament and more disarray.

Ms. May has had a tumultuous few days since returning from a summit of EU leaders last week in Brussels where she enraged some leaders by appearing inconsistent about her Brexit plans. Things only got worse over the weekend when an estimated one million people flooded central London to demand another Brexit referendum, something Ms. May has refused, and reports surfaced that a group of her cabinet ministers plan to call on her to resign.

Several media outlets reported that the ministers want Ms. May to be replaced as early as this week by a caretaker prime minister who could get the country through the immediate Brexit crisis. The Conservative Party would then hold a leadership contest in the fall to select a permanent leader who would take over as prime minister, according to the reports.

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Ms. May has faced leadership plots before and she won a vote of no confidence among Tory MPs last December, which means that she cannot be formally challenged for 12 months. Instead, the rebels would have to force her to step down. However, they don’t appear to have settled on an interim replacement. One of those named as a potential interim leader, David Lidington, the de facto deputy prime minister, dismissed the coup on Sunday. “I don’t think that I have any wish to take over from the PM, I think [she] is doing a fantastic job,” Mr. Lidington told reporters.

Philip Hammond, the Chancellor of the Exchequer, also lasted out at the plotters. “Changing prime minister wouldn’t help us,” he said Sunday. “To be talking about changing the players on the board, frankly, is self-indulgent at this time.” Environment Secretary Michael Gove, another potential replacement, told reporters it was "not the time to change the captain of the ship”. On Sunday Ms. May also tried to diffuse the concerns by meeting several Tory rebels.

But there has been growing angst about Ms. May in recent days among Tory Members of Parliament. Her authority has been so undermined that some cabinet ministers recently voted against government motions in parliament, something that under the British system would normally result in automatic resignation. The Prime Minister also infuriated MPs last week when she made a televised address to the country that blamed parliament for the Brexit chaos. On Sunday several Tory MPs came out against Ms. May and urged on ministers to rebel. “I’m afraid it’s all over for the PM,” Tory MP George Freeman said on Twitter. “She’s done her best. But across the country you can see the anger. Everyone feels betrayed. Government’s gridlocked. Trust in democracy collapsing. This cant go on. We need a new PM who can reach out & build some sort of coalition for a PlanB.”

Ms. May’s problem has been an inability to get a withdrawal agreement she struck with the EU approved by parliament. Members of parliament have rejected it twice by large margins with most of the opposition coming from the Tory party caucus and Northern Ireland’s Democratic Unionist Party, whose 10 MPs prop up Ms. May’s minority government. Ms. May had been planning to try once more this week, but she conceded on Friday in a letter to MPs that the chances of it being approved are so remote she may not even put it to a vote. Instead, MPs are expected to vote on a range of alternatives which include another referendum, a closer relationship with the EU or revoking Brexit altogether.

The Prime Minister asked EU leaders last week to extend the deadline for Britain’s departure from March 29 to June 30 in order to giver her time to get the deal approved. But after a night of intense discussion on Thursday, EU leaders would only agree to an extension to April 12. If the deal is not passed by then, Ms. May will have to present the EU with an alternative if she wants another extension. Many EU leaders expressed exasperation that Ms. May had no plan B and that at one point she backed the country leaving without a deal, contrary to her repeated statements which warned about the economic consequences of a no-deal Brexit.

“I think she will struggle to survive” as leader,” said Alex De Ruyter, a professor at Birmingham City University and is also Director of its Centre for Brexit Studies. “I don’t think she’s going to go of her own volition. I think she wants to be the person to choose when she departs.” Dr. De Ruyter added that even if Ms. May’s deal was approved, the uncertainty over Brexit wouldn’t end. That’s because the agreement includes a two-year transition period during which Britain would remain within the EU’s single market, which provides for the free movement of goods, people and services. During that time Britain and the EU are supposed to negotiate a comprehensive trade deal. “And of course at the end of that [two-year period] there could still be no deal in the sense that the two parties can’t come to an agreement over a future economic relationship. All this uncertainty will continue and of course that won’t help with business investment decisions.”​