London (CNN) The Brexit process was thrown into disarray Monday as Prime Minister Theresa May pulled the plug on a crucial parliamentary vote on her deal for the country to leave the European Union.

May admitted the decision to delay the vote was made after it became clear she would lose it "by a significant margin." She will now go back to EU leaders to seek further reassurances, she said.

The embattled leader told the UK House of Commons that she had listened "very carefully to what has been said in this chamber and out of it" -- a statement that was met with laughter and jeering by members of Parliament.

An emergency debate on the government's decision will take place in Parliament on Tuesday morning as "the first item of business," Speaker John Bercow said. Opposition Labour Party leader Jeremy Corbyn requested the emergency debate Monday night.

May admitted that "there remains widespread and deep concern" over the Northern Ireland backstop. The backstop is an arrangement designed to ensure there is no return to a "hard border" between Ireland, which will remain part of the European Union after Brexit, and Northern Ireland when the UK leaves the bloc next March.

Northern Ireland's secretary of state said she supported the decision to delay the vote.

"Clearly, having listened to colleagues across the House, there is more work to be done to provide reassurances on the Northern Ireland-Ireland backstop," MP Karen Bradley said in a statement. "I am convinced that leaving the EU without an agreement would be disastrous for Northern Ireland and potentially for the long-term future of the Union. I am not prepared to take risks with or gamble the Union of the United Kingdom."

The prime minister said she had hoped changes secured to the backstop, to avoid being trapped in it indefinitely, would be enough for MPs.

"I spoke to a number of EU leaders over the weekend and, in advance of the European Council, I will go to see my counterparts in other member states and the leadership of the council and the commission. I will discuss with them the clear concerns that this House has expressed," May said.

"We will therefore defer the vote scheduled for tomorrow and not proceed to divide the House at this time," May added.

On Tuesday morning May will travel to The Hague to hold a bilateral meeting with Dutch Prime Minister Mark Rutte, Downing Street said.

It will be part of May's plan to seek "assurances" from EU leaders, which she can then convey to the UK Parliament to pass her Brexit deal.

Opposition leader: Our country deserves better

Corbyn called her agreement a "botched deal" before adding that "our country deserves better than this."

"The government has lost control of events and is in complete disarray," Corbyn said. "It's been evident for weeks that the prime minister's deal did not have confidence of this House yet she plowed on regardless, reiterating 'this is the only deal available.'"

The leader of the House, Andrea Leadsom, confirmed the vote was no longer on the House voting schedule after May's statement.

The uncertainty over the future of Brexit caused sterling to plummet Monday to its weakest level in a year-and-a-half.

UK parliamentarians were supposed to be given the opportunity to approve or reject the deal in a so-called "meaningful vote" in the House of Commons on Tuesday evening.

In recent weeks, May had been trying to win support for her agreement but, with a high number of her own Conservative Party MPs opposed to it, she didn't appear to be having much success.

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EU: No further negotiations

There was confusion and anger as May hit the pause button on the vote.

European Council President Donald Tusk said the EU "will not renegotiate the deal including the backstop" and stressed that "as time is running out, we will also discuss our preparedness for a no-deal scenario."

Tusk added that the EU is "ready to discuss how to facilitate UK ratification."

I have decided to call #EUCO on #Brexit (Art. 50) on Thursday. We will not renegotiate the deal, including the backstop, but we are ready to discuss how to facilitate UK ratification. As time is running out, we will also discuss our preparedness for a no-deal scenario. — Donald Tusk (@eucopresident) December 10, 2018

In a post on Twitter before May spoke, EU Parliament chief Brexit negotiator Guy Verhofstadt expressed his frustration at the vote's stalling.

"This delay will further aggravate the uncertainty for people & businesses. It's time they make up their mind!" he wrote.

I can't follow anymore. After two years of negotiations, the Tory government wants to delay the vote. Just keep in mind that we will never let the Irish down. This delay will further aggravate the uncertainty for people & businesses. It's time they make up their mind! #brexit — Guy Verhofstadt (@guyverhofstadt) December 10, 2018

Earlier on Monday, the EU's top court ruled that Britain could unilaterally halt the formal process of leaving the bloc next year.

The European Court of Justice sided with the advice of its top legal officer, who declared last week that the UK has the power to withdraw its notification to leave under Article 50 of the Lisbon Treaty, without the agreement of other member states.

#ECJ: UK is free to unilaterally revoke the notification of its intention to withdraw from the EU -- Case C-621/18 Wightman #Brexit pic.twitter.com/KUOI2eQ48C — EU Court of Justice (@EUCourtPress) December 10, 2018

But May's government dismissed the ruling, with Environment Secretary Michael Gove telling the BBC that the UK will divorce the bloc regardless of the ECJ decision.

"We voted very clearly -- 17.4 million people sent a clear message that they wanted to leave the European Union," said Gove, a prominent Leave campaigner. "And that also means leaving the jurisdiction of the European Court of Justice," he said.

Bradley said the agreement secured by the prime minister "is in the best interests of the whole of the United Kingdom, including Northern Ireland."

"The EU wanted to split Great Britain and Northern Ireland into two different customs territories. This agreement ensures that there is one United Kingdom customs territory in which Northern Ireland is an integral part. And the deal means that there will be no hard border on the island of Ireland so that people can continue to lead their lives in the same way as they do today," Bradley said in her statement.

"Overall, the agreement fully respects the democratically expressed wishes of the people of the United Kingdom who voted by a majority in June 2016 to leave the European Union. It enables us to take back control of our laws, our money and our borders. And in the unlikely event that the future relationship with the EU is not fully agreed by the end of 2020 the UK will have the option of extending the implementation or transition period rather than entering the so-called backstop at all."