LONDON — British MPs rejected Prime Minister Theresa May's Brexit deal by a record-breaking 230 votes, shrouding the U.K.'s path out of the European Union with doubt.

The vote in the House of Commons — 432 against and 202 for — means that the Withdrawal Agreement struck between May's government and the EU in November last year has fallen at the first hurdle. It must be ratified by the U.K. and European parliaments before it can come into force.

May’s government will face a no-confidence vote in the House of Commons on Wednesday, spearheaded by opposition Labour leader Jeremy Corbyn. However, May’s Conservative Party and parliamentary allies are expected to continue to support her despite the scale of the defeat being the largest any government has suffered in modern history.

The previous record was set by Ramsay MacDonald's minority government in 1924, which lost a division by 166 votes.

The prime minister said that, if her government is not toppled Wednesday, she will seek cross-party talks aimed at finding a way forward that can secure a majority in the House of Commons, and pledged to reopen talks with the EU if an alternative strategy is agreed.

“Tonight’s vote tells us nothing about what [the House of Commons] does support, nothing about how or even if it intends to honor the decision the British people took in a referendum parliament decided to hold,” May told MPs after the vote.

She said that if she wins the vote of confidence, and if meetings with parliamentarians yield alternative ways forward, she will then “explore them with the European Union.”

The government must make a statement and bring forward a motion about its Brexit strategy by Monday. This will be amendable by MPs and will be a key test of May’s attempt to reach out across party lines.

With the U.K. legally required to leave the EU on March 29, May now has no choice but to return to Brussels seeking further talks on an agreement she calls the "only deal” that can deliver on the June 2016 referendum result while also avoiding an economically damaging no-deal break from the EU.

With protesters massed outside the Houses of Parliament — most pro-EU, but many pro-Brexit — May said ahead of the vote that MPs would be making “a decision that will define our country for decades to come.”

It is possible that she could bring her deal to a vote again in the coming days, after further talks with the EU, but Brussels has given no indication it is prepared to substantially alter the agreement.

May's deal was voted down by Labour and other opposition parties, but also by dozens of Conservative MPs and the Northern Irish Democratic Unionist Party, which props up her minority government.

The bulk of Conservative objectors are longstanding supporters of Brexit who are fearful that the deal's "backstop" provisions for avoiding an economic border between Northern Ireland, part of the U.K., and EU member the Republic of Ireland, could keep the U.K. too closely bound to EU regulations.

Meanwhile the House of Commons will try to seize control of the Brexit process by putting forward backbench proposals for a "plan B" in the hope of commanding majority support. An alternative Norway-style single market relationship and a second referendum are mooted by different factions.

If no alternative path is found, the U.K. could still leave the EU without a deal, a legal cliff edge that is predicted to cause major disruption to trade and cooperation with its European neighbors. The government has had to take contingency measures to prevent shortages of medicines and food.

Health and Social Care Secretary Matt Hancock defended the prime minister in the wake of the result. "She’s clearly the best person to lead this country to find a way through this difficult impasse. They clearly voted against the deal but not against the PM," he said.

He rejected the suggestion that the Article 50 negotiating period would need to be extended.

Leading Brexiteers, including former Foreign Secretary Boris Johnson, former Brexit Secretaries Dominic Raab and David Davis, and backbencher Jacob Rees-Mogg published what they called an alternative prime minister’s statement.

That calls for the U.K. to make the EU a take-it-or-leave-it offer of a free-trade agreement, and prepare to leave with no deal should it be rejected.

Carolyn Fairbairn, director general of the Confederation of British Industry, said that every British business “will feel no deal is hurtling closer” and a new plan is "needed immediately."