Theresa May is facing 48 hours of parliamentary warfare as the Prime Minister battles to get her Brexit legislation back on track.
The EU (Withdrawal) Bill returns to the Commons today (Tuesday 12 June) and Wednesday for crunch votes.
The bill passed through the House of Lords, where various amendments were added including continued membership of the European Economic Area, with peers defeating the government 14 times over the bill.
May set the tone for a tense two days as she warned Tory Remainers that if they defied her and backed Lords amendments to the landmark Brexit legislation it would weaken Britain's hand at the negotiating table.
In what was seen at Westminster as a boost for the government, a potential defeat on the customs union seemed less likely as a compromise amendment was put together by Remain backers Sir Oliver Letwin and Nicky Morgan, as well as Brexiteers Jacob Rees-Mogg and Sir Bill Cash, which called for "a customs arrangement" with the EU.
However, the compromise is only likely to delay a full-blown showdown on the customs union until trade legislation returns to the Commons in July.
Listen to peer Lord Newby discussing the amendments with Julia Hartley-Brewer above
Addressing a meeting of the backbench 1922 Committee on Monday, ahead of the key votes, the Prime Minister said: "We must think about the message Parliament will send to the European Union this week.
"I am trying to negotiate the best deal for Britain. I am confident I can get a deal that allows us to strike our own trade deals while having a border with the EU which is as frictionless as possible.
"But if the Lords amendments are allowed to stand, that negotiating position will be undermined."
But Jeremy Corbyn and his frontbench have tabled their own amendments to the bill, separate to the ones added by the Lords, asking for a new customs union.
"We cannot settle for this,” said Corbyn in a Facebook post.
“Labour will only vote for a final Brexit deal if it delivers a strong relationship with the Single Market based on full tariff-free access and ensures no loss of rights and standards.
"Together with a new customs union, that would ensure a strong and balanced package to protect UK jobs and living standards, put a floor under rights and protections and ensure no hard border."