EU Brexit negotiator Michel Barnier said the bloc is stepping up preparations for a chaotic "no-deal" departure after Parliament's actions left the bloc "fearing more than ever that there is a risk" of a cliff-edge departure.
DUP leader Arlene Foster, whose small party props up May's government in the Commons, also called for "fundamental change" to the Brexit deal.
"It would deepen division when we need unity, it would bring chaos when we need certainty, and it would bring delay when we need to move forward", she told MPs.
May's deal faces widespread opposition, primarily because of language created to prevent the reintroduction of border controls between Northern Ireland and the Republic of Ireland, which some fear will indefinitely tie Britain to the EU.
UKH chief executive Kate Nicholls said: "Tonight's (15 January) vote in parliament brings into stark reality the prospect of a no-deal Brexit, which would likely be disastrous for the British economy and a hospitality sector that is well-equipped to make a vital economic contribution as we leave the European Union".
For more on this story, watch 1 NEWS at 6pm. A number of her Cabinet ministers have already chose to step down in protest of her plan, and Conservative whip Gareth Johnson tendered his resignation on the eve of the vote. Labour legislator Tulip Siddiq delayed the scheduled cesarean birth of her son so she could attend, arriving in a wheelchair. It is hard to see how any Brexit plan can pass the House of Commons without the support of some of Labour's 256 lawmakers.
But MPs on both the Remain and the Leave wings of the party warned she needed to make major changes to the deal if she is to get it through the Commons.
"There is no doubt that by far the most preferred option for the European Union would be a thoroughly negotiated withdrawal deal".
December 19, 2018 - The European Commission starts implementing its "no deal" Contingency Action Plan, covering 14 areas where United Kingdom withdrawal without a deal would create "major disruption for citizens and businesses" in the remaining 27 EU states.
Still, most analysts predict May will survive because lawmakers from her Conservative Party are unlikely to vote against her, and the Democratic Unionist Party in Northern Ireland, which supports the government, has said it will continue to back the prime minister.
No deal scenario could make united Ireland more likely - May
She later branded the Irish border backstop "toxic" and said her party's 10 MPs would vote against the Withdrawal Agreement. The Federation of Small Business in Northern Ireland said time was running out to avoid "a chaotic no-deal".
May responded: "When they were [voting in the European Union referendum] I believe they did vote to ensure we continue to have a good trading relationship with our nearest neighbours in the European Union but also to improve our trading relationships with others around the world".
Parliament has given May until Monday to come up with a new proposal.
And if that Plan B should fall through, Brexit's long-term future gets exceedingly murky. That's because on March 29, 2017, May delivered a notification to the EU Council President, Donald Tusk, under article 50 of the EU's Lisbon Treaty.
An EU official, who asked not to be identified because of the developing situation, said that it was "Important that he is available and working in Brussels during the coming hours".
'That would stop no deal Brexit happening'.
In another emotional speech, Geoffrey Cox, a Conservative lawmaker and the attorney general, urged the chamber to back May's deal.
"Brexit is a disgrace for the British people and for the EU".
The defeat leaves May's position precarious.
Opening a debate on a no-confidence motion due to be held in the British parliament on Wednesday, Labour leader Jeremy Corbyn said Prime Minister Theresa is running a "zombie government". He did, and it will be debated on Wednesday.
May has no apparent intention of resigning, telling Parliament after the vote, "The House has spoken and this government will listen", and proposing talks between her party and the political opposition "to determine a way forward".
But with no clear majority in Parliament for any single alternate course, there is a growing chance that Britain may seek to postpone its departure date while politicians work on a new plan.