Peers in the unelected House of Lords voted on Wednesday 358 to 256 for an amendment requiring ministers to protect the rights of more than three million European Union and European Economic Area (EEA) citizens after Britain leaves the 28-member bloc.

Under the alteration, the government would be committed to guaranteeing that EU citizens living legally in Britain when the bill is passed "continue to be treated in the same way with regards to their EU-derived rights."

New obstacle for PM

The alteration thereby delays the bill which will empower Prime Minister Theresa May to trigger Article 50 of the Lisbon Treaty and begin two years of formal divorce talks between the UK and the EU.

The departure was prompted by June's referendum which saw 52 percent of the UK vote in favor of leaving the EU.

Prior to Wednesday's vote, however, May said her timetable for triggering Article 50 would not change.

"It is, indeed, my plan to trigger by the end of March," she told MPs.

'Can't do negotiations with people's futures'

A spokeswoman for the conservative government's Brexit department said in a statement that it was disappointed by the vote.

"We are disappointed the Lords have chosen to amend a bill that the Commons passed without amendment," the statement read.

"Our position on EU nationals has repeatedly been made clear. We want to guarantee the rights of EU citizens who are already living in Britain, and the rights of British nationals living in other member states, as early as we can."

On the contrary, Labour Party Brexit spokeswoman in the Lords, Dianne Hayter, said the amendment was crucial because Europeans living in Britain "need to know now, not in two years' time or even 12 months' time" what their rights are.

"You can't do negotiations with people's futures. They're too precious to be used as bargaining chips," Hayter said.

Return to the Commons

Despite Wednesday's vote, the amendment is not yet binding and must now be returned to the elected lower house, the House of Commons, where there is a good chance it will be rejected.

By leaving the EU, the UK will be withdrawing from the bloc's policy of free movement, which allows citizens of the bloc's 28 member states to live and work in any of the others.

As a result, some three million EU nationals in Britain, and 1 million Brits in other member countries still remain uncertain as to whether they will be able to stay in their jobs and homes once Britain reasserts control over EU immigration.

May's Tory government has repeatedly claimed that it plans to guarantee the right of EU citizens to remain in Britain, as long as UK nationals living elsewhere in the bloc get the same right.

Critics, however, have accused the government of treating people as bargaining chips in the Brexit negotiations. 

ksb/jm (AFP, AP, Reuters, dpa)