Britain's prime minister Theresa May suffered a second defeat in parliament in two days as parliamentarians voted against her Brexit proposals.
Rebellious Conservative MPs teamed up with opposition party Labour on Wednesday to vote for a motion designed to prevent the government delaying key decisions on Brexit.
If Mrs May's Brexit withdrawal agreement is rejected in a crunch vote in the House of Commons next week then the government must reveal its "Plan B" within three days.
The government lost the amendment to a business motion, which set out the procedure for the Brexit vote, by 11 votes with 297 MPs voting with them and 308 against.
Downing Street played down the impact of the vote, which reduced the time limit for the government to respond from 21 days.
"We are doing everything we can to win the meaningful vote that happens on Tuesday," the prime minister's spokesman said.
"But it is also the intention, if that were not to take place, that we respond quickly to provide certainty on the way forward following that vote."
On Tuesday evening, Mrs May lost a vote on an amendment to a finance bill, which was designed to limit the government's powers in the event of a no-deal Brexit.
While the two votes are largely symbolic, the successive defeat shows how weak parliamentary support is for Mrs May's Brexit plans.
The Democratic Unionist Party have said they will not support her deal in the crunch vote next week. The vote had originally been slated for December but was postponed after it became clear the government would be defeated.
Mrs May's attempts to win over MPs were further thwarted on Wednesday after the DUP dismissed new assurances over the controversial backstop element of the withdrawal agreement as "meaningless".
The backstop, which would only come into force if no agreement on trade was reached during the transition period, would see Northern Ireland tied to some of the EU's rules.
The government published pledges offering Northern Ireland a "strong voice and role in any decision to bring the backstop into effect".
But the DUP, which is propping up Mrs May's minority government through a confidence and supply agreement, immediately rejected the offer.
The DUP's Brexit spokesman Sammy Wilson said: "The only thing which could swing the DUP round is if the backstop as it applies to the United Kingdom as a whole or to Northern Ireland specifically were removed from this agreement."
Mrs May has repeatedly said the UK will leave the EU on March 29, 2019.
In a warning to pro-Remain MPs on Wednesday, cabinet minister David Lidington said if Mrs May's Brexit deal was rejected, the UK would leave without a deal.
Mr Lidington told the BBC that no alternative deal would be negotiated.
MPs have just begun five days of debate on the Brexit agreement ahead of the crunch vote on January 15.