Theresa May faces a defeat in the House of Lords after refusing to write into legislation a Post-Brexit guarantee for EU citizens currently in Britain.

Lords wanted a clause in Ms May’s bill to trigger Article 50 stating that EU citizens already in the UK will have the same rights to live and work here after Brexit.

But a letter from Home Secretary Amber Rudd seen by The Independent says the Government will not go further than giving verbal assurances it has already given.

With a face-off over the matter expected on Wednesday, Lords are now likely to push the matter to a vote and defeat the Government – with Tories in a minority in the upper House, and Labour, Lib Dems, cross-bench peers and potentially rebel Tories united on the issue.

After Ms Rudd’s letter was sent to Lords, a Labour source said: “They are going to dig in.

“They are trying to buy off the vote on Wednesday, just by saying that people’s rights will be protected. Now there’s going to be a vote, it will likely end up in a Government defeat.”

Ms May’s bill to trigger Article 50 passed through the Commons unamended, but faces attempts to change it over several issues in the Lords including on EU citizens’ rights and guaranteeing Parliament a final vote on Ms May’s Brexit deal – the “meaningful vote amendment”.

But with the issue of EU citizens set to come to a head in the Lords on Wednesday, Ms Rudd wrote that no guarantee could be given to EU nationals until official Brexit talks are agreed and a similar guarantee is given to Brits living in Europe.

She said: “There is absolutely no question of treating EU citizens with anything other than the utmost respect. That’s why we will be making securing their status a priority as soon as we trigger Article 50 and the negotiations begin.

“Strong views have been expressed about the wish for the Government to move unilaterally on this issue. As Lord Lamont said during Second Reading of the bill, a unilateral move by the Government to address the issues facing EU nationals in the UK, however well intentioned, will not help the situation of the hundreds of thousands of our own citizens in the EU.”

In response to the Home Secretary’s letter on EU citizens’ rights in the UK, Labour’s leader in the House of Lords, Baroness Angela Smith of Basildon said: “To continue to use people as bargaining chips in this way is not only shameful but could have a dire impact on the UK’s economy and essential services.

“Confirming the rights of those EU citizens living in the UK can only be of benefit to our citizens worried about their future in EU countries but the Government’s approach seems to be to sit back and wait for others to blink first."

Liberal Democrat Leader Tim Farron said the Government was determined to use the 3.3 million EU citizens in the UK as “bargaining chips” in Brexit talks.

He added: “The fact is that the UK Government can and should act unilaterally to secure the rights of EU citizens here in the UK, and all open and tolerant people in the Lords should support the cross party amendment to do that.