British Prime Minister Theresa May confirmed on Monday that she has postponed a crucial parliament vote on her Brexit deal with the European Union, which had been due to take place on Tuesday.

Over the next few days, she will visit her counterparts in other member states to discuss the concerns that Parliament has expressed.

In an address to parliament, she said she was ordering the delay because the deal was set to be rejected "by a significant margin".

"It is clear that while there is broad support for many of the key aspects of the deal, on one issue, the Northern Ireland backstop, there remains a widespread and deep concern," May said.

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

Her address was met by shouts from MPs.

Just hours earlier, May's spokesperson told the press that the vote would definitely go ahead.

British bookmakers predicted a 95% chance the House of Commons would vote against passing the draft Brexit agreement, which would catapult May's leadership ability into question.

Sterling plummeted to an 18-month low against the US dollar amid reports of May backing out of the vote, according to Reuters. It further dropped to a 20-month low as May confirmed her decision to delay the vote.

What has been the official reaction?

Opposition Labour leader Jeremy Corbyn called the delay a "desperate step" from the British government at the 11th hour.

"We have known for at least two weeks that Theresa May's worst of all worlds deal was going to be rejected by parliament because it is damaging for Britain," he wrote on Twitter. "Instead, she ploughed ahead when she should have gone back to Brussels to renegotiate or called an election so the public could elect a new government that could do so."

Scotland's first minister, Nicola Sturgeon, tweeted directly to Corbyn, suggesting a potential partnership to campaign for a second referendum.

Encouraging the labour leader to file a motion of no confidence in May, Sturgeon tweeted to Corbyn: "we can then work together to give people the chance to stop Brexit in another vote."

"This shambles can't go on — so how about it?"

In an earlier tweet, Sturgeon said a confirmation of a delayed vote would be evidence of "pathetic cowardice" from May. "Yet again, the interests of the Tory party are a higher priority for her than anything else," she added.

Junior Minister Nadhim Zahawi tweeted amid the chaos, saying May planned to return to Brussels to renegotiate the backstop, the part of the deal regarding the Irish border.

However, the European Commission said on Monday it was not open to renegotiating the agreement made with May.

"We have an agreement on the table," a spokeswoman for the European Commission told reporters. "We will not renegotiate."

European Council President Donald Tusk echoed the sentiment from the European Commission, saying a renegotiation was off the table, including any negotiating on the Irish backstop, but that the EU would be open to discussions on how the current deal could be implemented, and preparations for a no-deal Brexit.

Over in Northern Ireland, the Democratic Unionist Party leader Arlene Foster said she had spoken to May on the phone, and urged her to drop the Irish backstop agreement.

"My message was clear. The backstop must go," Foster said. "Disappointed it has taken so long for the prime minister to listen."

However, Leo Varadkar was quoted in Irish media as saying earlier on Monday that the current draft agreement, which includes the backstop, "is the only agreement on the table."

Guy Verhofstadt, the Brexit coordinator for the European Parliament, commented on his exasperation over the latest updates from the UK.

"I can't follow anymore," he wrote on Twitter. "After two years of negotiations, the Tory government wants to delay the vote."

Referring the backstop part of May's deal, Verhofstadt said the EU would "never let the Irish down."

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

READ: What could happen after MPs vote on the Brexit deal?

READ: What is in Theresa May's Brexit deal and why is it so unpopular?

READ: Brexit Borders - how Brexit is seen on the Scottish border

To see how events unfolded, follow our live blog below: