London (AFP) - The House of Lords voted Wednesday to amend and thereby delay a bill empowering Prime Minister Theresa May to begin Brexit negotiations, demanding guarantees for EU nationals living in Britain.
In a major defeat for the government, peers voted by 358 to 256 for an amendment requiring ministers to protect the rights of more than three million European citizens after Britain leaves the bloc.
The change means the bill must return to the lower House of Commons for deliberation, delaying final approval just weeks ahead of May's deadline for starting Brexit negotiations by the end of this month.
Before the vote, May said her timetable for triggering Article 50 of the European Union's Lisbon treaty, which starts a two-year negotiating period, would not change.
"It is, indeed, my plan to trigger by the end of March," she told MPs.
A Brexit ministry spokesman said it was "disappointed" at the Lords vote, which comes after MPs overwhelmingly approved the bill last month. Lawmakers in the lower house defeated all amendments to the bill, including one on the rights of EU nationals.
Opposition Labour leader Jeremy Corbyn welcomed Wednesday's vote as "great news" on Twitter, suggesting he may support the amendment when it returns to the lower house.
A spokeswoman for May's office told AFP the government would seek to reverse the change when it moves back to the Commons, where May's Conservatives have a majority.
If they succeed, the original bill would go back to the Lords in what is known as parliamentary ping-pong.
The delay may only end up being a few days, but the defeat signals the domestic opposition that May could face during the next two years of complex EU negotiations.
- 'Lives on hold' -
The June referendum vote was fuelled by concerns about mass EU migration into Britain, and immigration promises to be a critical issue once negotiations begin.
May has said she will prioritise ending free movement of workers from the other 27 EU countries, even at the cost of trade ties with the bloc.
But the fate of those who are already in Britain remains uncertain, causing intense worry for people affected.
The prime minister has repeatedly said she wants them to stay, but says she must also secure the rights of 1.2 million British citizens living elsewhere in the EU.
Labour party peer Baroness Dianne Hayter said the amendment was tabled on behalf of "three million people who quite literally feel they are being used as mere bargaining chips".
She rejected May's argument that she must wait for a reciprocal deal, saying: "These two groups of people should not be traded against each other."
She added: "These people need to know now, not in two years' time or even 12 months' time. They simply can't put their lives on hold."
- 'Common goal' -
May was forced to introduce the Brexit bill after the Supreme Court ruled she could not trigger Article 50 without parliament's approval, sparking fears that pro-European lawmakers would use the opportunity to block Brexit.
Unlike in the Commons, May's Conservative party is in the minority in the 800-seat House of Lords, and Labour's amendment had cross-party support.
Former Conservative minister Quintin Hogg had backed it, urging peers to "take the moral high ground".
Another former Tory minister, Lord Norman Tebbit, was jeered when he said the debate seemed to focus on "nothing but the rights of foreigners".
May had hoped to agree a deal on EU nationals late last year, but European leaders insisted there could be no talks on any subject before the government triggers Article 50.
"The hold-up is less an issue of principle than one of timing," Home Secretary Amber Rudd wrote to peers on the eve of the vote in a bid to fend off the defeat.
"However, I believe the UK and the EU have a common goal to provide this assurance as quickly as possible."
The government risks defeat on another amendment due for consideration in the Lords next week, on giving parliament a vote on the final withdrawal deal.
May has given verbal assurances that such a vote will take place, but her opponents want this enshrined in law.