Facing a very real chance that her Brexit deal will be rejected in a House of Commons vote on Tuesday, embattled U.K. Prime Minister Theresa May said the country is in "uncharted waters" and warned lawmakers about the risk of a no-deal Brexit — something most economists believe would be catastrophic for the country.

The country's Brexit Secretary, Stephen Barclay, has said the Commons vote will not be delayed, reports the BBC. Voters in the United Kingdom decided in June of 2016 to leave the European Union after having been a member since 1973, although some polls taken since have shown that most Brits would now choose to stay in the EU.

Meanwhile, the prime minister warned lawmakers that rejecting the deal could trigger a general election.

Although the withdrawal deal negotiated between European Union leaders and the U.K. has been agreed to by the EU, the British government is expected to lose next week's vote with Labour, Liberal Democrats, the DUP, the SNP and dozens of conservative lawmakers saying they cannot support the deal.

"When I say if this deal does not pass we would truly be in uncharted waters, I hope people understand this is what I genuinely believe and fear could happen," May told the Mail on Sunday.

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Protestors demonstrate opposite Parliament against Britain's Brexit split from Europe, in London, Thursday, Dec. 6, 2018.  (AP)

She told the British newspaper that rejecting her deal would "mean grave uncertainty for the nation with a very real risk of no Brexit or leaving the European Union with no deal."

Esther McVey, who quit May's cabinet over the deal, agreed with former Foreign Secretary Boris Johnson, telling Sky News that May should "immediately" renegotiate with Brussels if her deal is rejected.

In addition, three of the largest donors to the Leave campaign told Sky News that it would be better for Britain to remain in the EU than sign up for May's Brexit deal.

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For Labour, the BBC reports that Shadow Brexit Secretary Rebecca Long-Bailey would not confirm that Labour would immediately put down a motion of no confidence in Prime Minister May if the deal gets rejected.

She told the BBC: "We will have to see what happens on Tuesday... we will have to make an assessment at the time and we will be in discussions with other political parties across the House to assess the best thing to do."

Britain's Prime Minister Theresa May, under fire for her handling of Brexit, attends the ceremony to light up a Christmas tree at 10 Downing Street in London, Thursday, Dec. 6, 2018. (AP Photo/Frank Augstein)

Johnson told Sky News that he doesn't want a second referendum, which is what some have called for if the Tuesday vote fails, saying it would be "extraordinary" to have another vote before the first has even been implemented.

Meanwhile, the cross-party Commons Committee on Exiting the European Union said this weekend that the Brexit deal is a "huge step into the unknown."

EU leaders have insisted the divorce agreement is final and not renegotiable. However, while the 585-page withdrawal deal is set, the declaration on future relations between the EU and Britain is shorter and vaguer and may be open to amendment.

The Associated Press contributed to this report.