British MPs voted Wednesday to force Prime Minister Theresa May to quickly set out an alternative plan for Brexit if she loses a crucial vote on her EU withdrawal deal next week, in a second parliamentary defeat in 24 hours.
The House of Commons voted to reduce the time the government has to explain its "plan B" from 21 sitting days to three if, as expected, lawmakers reject the draft Brexit agreement in a vote on Tuesday.
Members of May's own Conservative party led the revolt amid fears that delaying the decision raises the risks of Britain crashing out of the European Union on March 29 with no deal at all.
It was the second setback in as many days for the prime minister, after MPs voted late Tuesday to deny the government certain taxation powers in a no-deal scenario - another attempt to avoid such an outcome.
Speaking to MPs earlier, May said: "The only way to avoid no deal is to vote for the deal."
But her spokesman added: "If that were not to take place... we would respond quickly and provide certainty on the way forward."
The parliamentary manoeuvres came at the start of five days of debate on the deal May struck with the EU last November, which has been strongly opposed from lawmakers on all sides of the House of Commons.
She set out further clarifications she hopes will win over her own Conservative MPs and Northern Ireland's Democratic Unionist Party (DUP), which props up her government in parliament.
The most controversial element of the agreement is the "backstop" arrangement, which could see Northern Ireland continue to follow certain EU trade rules after Brexit to avoid border checks with Ireland.
The government has now offered guarantees to local lawmakers in the province over the operation of the backstop, and on the free flow of trade between Northern Ireland and mainland Britain.
But DUP deputy leader Nigel Dodds said the proposals were "meaningless and cosmetic", adding he would keep pressing for changes to the overall deal.
May is also still seeking assurances on the operation of the backstop from European leaders, which she hopes to deliver before the vote next week.
The prime minister has already postponed the vote once - in December - to avoid defeat, and has said a loss for the government would plunge Britain into "uncharted territory".
But without the DUP's support, and with many of May's Conservative MP still strongly opposed, the deal cannot pass.
No deal fears
The prime minister has warned that defeat will lead to a no-deal Brexit, or possibly no departure from the bloc.
Both revolts this week have been driven by Conservative MPs who fear what they see as the potentially disastrous impact of leaving the EU in March with no arrangements in place to replace four decades of membership.
Late on Tuesday, 303 MPs - among them more than a dozen former Conservative ministers - voted to restrict the government's taxation powers in a "no deal" scenario, against 296 who backed May.
The government said it was an "inconvenience" but would not stop preparations for leaving the EU.
Wednesday's amendment has more weight, requiring May, is she loses the divorce deal vote, to explain her "plan B" by the latest on Monday, January 21. It passed by 308 votes to 297.
"The government's decision to delay the meaningful vote has run down the clock and increased the risk of a no deal Brexit," Labour's Brexit spokesman Keir Starmer said.
"If the prime minister's Brexit deal is defeated next week, she must return to parliament as soon as possible and give MPs a real say on what happens next."
There was a major row in the Commons over whether the amendment could even be put to a vote, with Speaker John Bercow apparently disregarding the advice of his own clerks that it could not.
Several Conservative MPs accused Bercow of being biased against Brexit, but he insisted he was only supporting the right of MPs to challenge the government.
Labour has said it will seek a confidence vote in the government if it loses next week, and leader Jeremy Corbyn demanded she "do the right thing" and call a general election.
Conservative lawmaker and former minister Ken Clarke meanwhile repeated his call for Brexit to be delayed while parliament decides what to do next.
Despite the support of a majority of MPs to avoid a "no deal" scenario, without agreement on an alternative Britain is legally on course to leave the EU in March unless it delays or cancels the process.
May insists Brexit will happen in March, but there is growing talk of delaying the two-year Article 50 exit process.