UK Members of Parliament (MPs) are set to vote on whether to block the UK from leaving the EU without a deal on 29 March, after again rejecting the PM’s withdrawal agreement.
The deal was defeated in the Commons on Tuesday evening by 149 votes.
The government will publish guidance for businesses on tariffs and proposals for the Irish border in the event of no deal on Wednesday morning. The cabinet is due to meet at 08:00 GMT.
The EU said no deal plans were “more important than ever” after the defeat.
Numerous EU leaders expressed their dismay after MPs voted by 391 to 242 votes to reject May’s deal.
The prime minister said Tory MPs will get a free vote on Wednesday evening’s motion.
That means Tory MPs can vote with their conscience rather than following the orders of party managers – an unusual move for a vote on a major policy.
The motion says: “This House declines to approve leaving the European Union without a withdrawal agreement and a framework on the future relationship on March 29.”
If no-deal is rejected, MPs will vote on Thursday on delaying Brexit by extending Article 50 – the legal mechanism that takes the UK out of the EU.
The EU has said it would need “a credible justification” before agreeing to any extension.
Leaving the EU in 16 days’ time remains the UK’s default position under the law.
In the Commons on Tuesday evening, Labour Party leader Jeremy Corbyn said Mrs May should now call a general election.
The PM had made a last-minute plea to MPs to back her deal after she had secured legal assurances on the Irish backstop – the insurance policy to stop a hard border on the island of Ireland – from the EU during late-night talks in Strasbourg on Monday.
He called for no-deal to be “taken off the table” – and said Labour would continue to push its alternative Brexit proposals.
But he did not mention his party’s commitment to back another referendum.