The Prime Minister has told her Cabinet the government will launch a "robust response" to the amendments waved through by the House of Lords last night.
Three amendments to the EU Withdrawal Bill were approved by peers yesterday, including one which could force negotiators back to Brussels if the final deal is not approved.
During this morning's Cabinet meeting, ministers including Brexit secretary David Davis expressed their "strong disappointment" with the vote, adding: "We wish for the bill to go through in the same way it left the Commons."
Prime Minister Theresa May promised her top team the government would be "robust in its response". The government will try to persuade MPs to overturn the change when the bill returns the Commons later this month.
Speaking this afternoon, a Downing Street spokesman said there would now be a discussion around how to respond to the specific amendments, noting that some of the previous amendments put forward by the upper house simply required the government to "provide a report", whereas there have now "been amendments that wouldn't allow us to bring forward a smooth Brexit, or would tie our hands in talks".
Already the act has been slammed by international trade secretary Liam Fox, who told the Today Programme the "unelected house" were trying to "thwart the will of the British people".
However there appears to be some confusion as to what exactly the amendment offers above and beyond normal processes.
While Number 10's spokesman insisted the government had been "very, very clear" that the final vote would be "deal or no deal", Davis last week admitted parliamentarians would have the right to amend the final deal via the Withdrawal Agreement and Implementation Bill, which will be brought forward after heads of terms have been agreed this autumn.
He told Hilary Benn's Exiting the EU Committee: “If you can tell me how to write an unamendable motion, I will take a tutorial.", later warning: "I'm not entirely sure how much force a government sent back with its tail between its legs by Parliament would have in such a negotiation."