The U.K.’s upper house sought to make it harder for Prime Minister Theresa May to take Britain out of the European Union without a deal by defeating her for a seventh time over the government’s flagship Brexit legislation.

The House of Lords voted 335 to 244 in favor of an amendment to the government’s European Union (Withdrawal) Bill to give Parliament a vote before May can walk away from negotiations with the EU without a deal. It was sponsored by peers across the political spectrum: former Conservative Cabinet minister Douglas Hogg, Labour’s Dianne Hayter, William Wallace of the Liberal Democrats, and David Hannay, an independent.

“Whatever the outcome, terms, or no terms, this country’s future should be determined by Parliament, ultimately by the House of Commons, and not by ministers,” Hogg told peers on Monday.

The defeat is yet another headache for May, coming less than 24 hours after Home Secretary Amber Rudd resigned for “inadvertently” misleading lawmakers over immigration targets — depriving the prime minister of a key ally on Brexit. Brexit Minister Martin Callanan told the Lords that the “true motivations” of many of the amendment’s supporters was “thwarting Brexit.”

‘Perverse’

“This amendment will bolster those who wish not to secure the best deal with the EU, but rather who wish to frustrate Brexit altogether,” he said. “It would create a perverse negotiating incentive for the EU to string out negotiations for as long as possible. It is not in the U.K.’s interest to hand the EU negotiators a ticking clock and the hope that the more they delay, the more they can undermine the position of the U.K. government.”

Monday’s amendment builds on one put forward in the House of Commons by former Attorney General Dominic Grieve, May’s sole defeat on the legislation so far in the lower chamber.

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A dozen Tory lawmakers — dubbed “mutineers” by the pro-Brexit press — rebelled on that vote, showing there may be appetite in the lower chamber to support the Lords amendment as well.

“We and others seek to ensure our country’s future should be determined by Parliament,” Hayter, Hannay and Wallace wrote in the Independent newspaper on Monday. “It seems extraordinary that we should even have to argue that case. Even more so that we should be called mutineers or saboteurs for upholding democratic principles.”

No Protection

Leaving the EU without a deal would mean no protection for U.K. citizens living in the bloc, no rights for EU citizens living in Britain, a hard border between Northern Ireland and the Republic of Ireland, and “immediate customs duties on the flow of goods,” the three peers wrote in the Independent. “Any such outcome must be taken by Parliament, not just ministers.”

Hogg went even further, saying that without Monday’s amendment, “Parliament will not have a genuine, meaningful vote” on the Brexit deal.

He argued that Parliament should be able to vote on whether to leave the EU on May’s terms, and if it rejected them, there would be three options: instruct her to renegotiate a new deal, choose to stay in the bloc on current terms, or leave the EU without a deal.

As with May’s previous defeats in the upper chamber, the amendment can be overturned when the bill returns to the House of Commons at a date yet to be specified. The earlier amendments include:

Peers voted April 25 to deny ministers of powers May hoped to grant them to alter regulations after Brexit On April 23, May lost votes on amendments to ensure EU rules from the Charter of Fundamental Rights are written into U.K. law, as well as retaining the right to legal action over any failure to comply with the general principles of EU law The government lost a vote on April 18 on an amendment pressing it to seek a post-Brexit customs union with the EU

Monday’s session was the fourth of six in the House of Lords on May’s Brexit bill, with further debates on May 2 and May 8. Hayter has said she can also envisage defeats for the government on Northern Ireland and removing the government’s fixed Brexit day of March 29, 2019 to give added flexibility.