Jeremy Corbyn will step up pressure on Theresa May to guarantee the status of EU nationals in the UK after Brexit amid growing confidence in Labour they can force a Government concession on the issue.
In a speech in London on Friday, Mr Corbyn will vow to do everything possible to stand up for the rights of EU citizens living in Britain, accusing ministers of treating them as a "bargaining chip" in the forthcoming negotiations on British withdrawal.
"The rights of EU nationals living and working in Britain must be guaranteed now, just as the rights of UK nationals must be protected across the rest of the EU," he will say.
"It is a scandal that our government is trying to use citizens of the EU, who have made their homes in Britain, as a bargaining chip.
"I understand the fear in many communities since the Brexit vote.
"Many EU nationals feel isolated and believe they are no longer welcome in the country they have come to call home."
His intervention comes as Labour sources said there was growing cross-party support for an amendment they have tabled party to the Brexit Bill currently going through Parliament, calling on the Government to guarantee the position of EU nationals.
The Tory peer Lord Bowness has now joined the Liberal Democrats in backing the proposed change to the legislation, which returns next week to the House of Lords, a move which Labour believes reflects wider concerns within the Conservative ranks.
Labour's leader in the Lords, Baroness Smith of Basildon told The Guardian: "My sense is there's real momentum behind this one, and my sense talking to peers across the house and listening to the debate, is this is something that the House of Lords would support, cross-party."
Ministers have resisted demands, including from many Tory backbenchers, to secure the position of EU nationals ahead of the Brexit negotiations arguing they need to secure reciprocal rights for British nationals living in the EU.
While the Government does not have an overall majority in the Lords, it could seek to overturn any amendment passed by peers in the Commons.
However Labour sources said they believed they would have to come forward with some changes of their own if they were to satisfy their own backbenchers who are becoming increasingly restive on the issue.
Labour is also hopeful of forcing a further concession over their demands for the Government's promise of Parliament will have a chance to vote on any Brexit deal with the remaining 27 EU member states before it is finally agreed.
It follows a warning from the former Supreme Court judge Lord Hope of Craighead, that the legislation as is standing may not be sufficient to satisfy the court's ruling that Parliament was entitled to a say on Brexit.
Lady Smith said Labour was confident of winning a vote in the Lords on an amendment drafted in the light of comments by Lord Hope and other experts in the upper chamber.
"The Government of course could try to overturn it in the Commons," she said.
"But rather than ministers just holding to the line that they won't amend the Bill but will make a statement on the record, it would be a positive and mature signal for future progress of legislation if having accepted the principle they write this into the Bill."
A Downing Street spokesman said: "The PM has been very clear that we want to guarantee rights of EU citizens in this country and we want there to be reciprocal arrangements for UK citizens in other member states and we want this to be one of the things that is addressed early in the process."