Boris Johnson is braced for a Lords defeat on his Brexit bill amid disquiet among Tory peers over the decision to strip support for child refugees from the legislation.

Labour peer Alf Dubs has tabled a new amendment to ensure protections for child refugees remain in the Withdrawal Agreement Bill (WAB) – a promise made by Theresa May but noticeably absent from Mr Johnson’s new bill.

Despite being summoned to meet Home Office ministers and No 10 officials this week, Lord Dubs, who fled the Nazis as a child on the Kindertransport, was undeterred in his efforts to ensure the right of family reunion for unaccompanied children.

The Labour peer said a number of Tory peers – including ministers – were unhappy about removing the commitment from the bill and may abstain to help the opposition next week.

Lord Dubs told The Independent: “All I can say is that there are quite a lot of Conservative members of the Lords who are unhappy about this. They won’t vote or speak but they may abstain, which will help.

“Some of them are government ministers and they are trying to lobby the government behind the scenes.

“It’s interesting how many Conservative peers are quietly supporting the amendment ... clearly the majority is not with the government.”

Lord Dubs said ministers tried to convince him to ditch his amendment by promising to enshrine protections for unaccompanied child migrants in a separate immigration bill.

He said: “This is too pie in the sky. I am not at all convinced. They said they wanted to have more flexibility for negotiating [with Brussels] but I don’t see this as up for negotiation.”

Lord Dubs added: “You are talking about children who are in desperately difficult circumstances, in what is left of the camps, sleeping under tarpaulins at Calais or in awful circumstances on Lesbos.”

Armed with an 80-strong majority, the prime minister fast-tracked the bill through the Commons unamended earlier this month.

However the government is braced for a battle in the Lords, with four amendments tabled by cross-party peers which could send force Mr Johnson’s bill back to the Commons.

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Opposition sources in the Lords have told The Independent that they are confident of the numbers to win, which they hope will pressure Tory MPs to shift when the legislation returns to the Commons.

There are also three other cross-party efforts gathering support, including amendments on citizens’ rights and sovereignty of the devolved nations.

Lord Pannick, the senior lawyer, has also tabled an amendment to scupper powers for ministers to direct British courts on interpretations of EU law, which caused alarm among some legal experts.

Baroness Hayter, shadow Brexit minister, told The Independent: “None of what is being proposed in these cross-party amendments will stop Brexit happening later this month.

“Indeed, they would strengthen the role of parliament, preserve the distinction between the power of the courts and the executive, acknowledge the Sewel convention and safeguard the wellbeing of both EU citizens and child refugees.

“The government would do well to heed concerns from across the House of Lords, rather than cock a tin ear towards the amendments.”

A No 10 spokesperson said: “The Withdrawal Agreement Bill reaffirms our commitment to protecting vulnerable children while clarifying the role of parliament and government in negotiations.