Labour peer says there is 50% chance they will vote on Wednesday on amendment to secure rights of EU citizens living in UK

Labour peers say they are confident that the government will ultimately make concessions as the article 50 bill on leaving the EU passes through the House of Lords this week.

Opposition whips will watch keenly how the government responds to the first debate at the committee stage of the bill on Monday, which will focus on the Good Friday agreement, to gauge whether the government appears open to concessions, one Lords source said.

Though no votes are planned until the report stage of the bill next week, one Labour peer said there was at least a 50% chance that peers could vote on an amendment to secure the rights of EU citizens living in the UK during the committee stage on Wednesday. “I would expect us to win that comfortably with the support of the Lib Dems, some cross-benchers and a handful of Tories,” the source said.

Dick Newby, leader of the Liberal Democrats in the Lords, said among peers there was “an overwhelming desire to do the right thing and ensure that all EU nationals have the right to remain”.

Opposition peers estimate about a dozen Conservatives are willing to be “unhelpful” to the government, though only four are known to be planning to vote against the bill or back opposition amendments – Peter Bowness, Ros Altmann, Patience Wheatcroft and Michael Heseltine.

Tory grandee Lord Heseltine has said he will back a Labour-led amendment to ensure a meaningful vote on the final deal, saying he simply wanted to uphold the supreme court’s ruling that MPs and peers had ultimate authority.

Though Labour Lords sources insisted they will not ultimately block the bill, they remain confident the government will make some concessions, including to pressure from their own backbenchers. “The bill will be changed when it goes for royal assent,” the Labour source said.

“Those 137 words will be different in two weeks’ time. We may not get our amendments, but when Tory MPs’ postbags are filling up with stories of EU citizens who have lived here all of their lives, they may think ‘why go through the pain?’ and if enough pressure builds up, we’d expect the government to come forward with their own words to change the bill.”

However, Tory party chairman Sir Patrick McLoughlin has insisted the Brexit bill should go through the Lords without peers making any changes to it. “We will want to see how the bill evolves once it’s out of the House of Lords,” he told the BBC’s Andrew Marr Show.

Asked if the government was ready for a fight with peers, he said: “We’ll see whether we’re going to have a fight or not. The bill should go through as it has come from the House of Commons, the elected House of Commons.”

A No 10 source said the prime minister’s approach would be to persuade peers of the merits of an unamended bill rather than attempt to “pick a fight”.

“We are going to carry on making the arguments that this bill does not need amendments, it does what the British people want,” the source said. “We believe in the strength of the argument, I don’t think peers do want to block the bill in totality. That is not what Labour want and we don’t even know what amendments are going to be read, let alone be successful.”