The Government has been heavily defeated in the Lords as peers backed a move to ensure the rights of unaccompanied child refugees to be reunited with their families in the UK post-Brexit.

Voting was 300 to 220, majority 80, in report stage debate on the European Union (Withdrawal Agreement) Bill, which has already been passed by big majorities in the Commons.

It was the fourth defeat for ministers on the legislation in less than 24 hours but is likely to be overturned by MPs when it goes back to the Commons on Wednesday.

Labour’s Lord Dubs led the bid to restore the right of unaccompanied child refugees in the EU to be reunited with their families in the UK after Brexit, suggesting his amendment would help disprove accusations that the Tories were the “mean and nasty” party.

The Labour peer, who fled the Nazis as a child on the Kindertransport, urged ministers not to use the small number of children involved as “bargaining chips” in negotiations.

He said the Government was seeking to delete earlier protections for child refugees in the EU (Withdrawal) Act 2018 but it was a simple matter of humanity to retain them.

Urging the Government not to “close the door” on the children affected, Lord Dubs said some lived in “shocking” conditions in French camps at risk of sexual exploitation.

By providing them with a safe, legal route to the UK, peers would be “thwarting the traffickers” and avoiding the need for youngsters to take more dangerous options to get to their families.

The Bishop of Durham, the Rt Rev Paul Butler, said the law as it stood was “hard fought for, not easily won”.

The bishop said the issue was a “moral bellwether for the future of our country”, adding: “We want to be known as a country that is welcoming and passionate and committed to playing our full part in responding to the deep issues that arise from the reality of refugees around the world.”

Liberal Democrat Baroness Hamwee said: “There is a strong feeling that Parliament should not reduce our commitment to these children or to safe and legal routes.”

Home Office minister Baroness Williams of Trafford urged peers not to press the issue to a vote.

Lady Williams said the Conservatives’ record of the last 10 years clearly demonstrated a commitment to protecting vulnerable children and this would continue.

She said more than 41,000 children had been granted protection in the UK since 2010 and over 5,000 unaccompanied children were being cared for in England alone.

The election manifesto underlined the commitment to continue to grant asylum and support for refugees fleeing persecution, Lady Williams added.

Labour, Liberal Democrat and crossbench peers ignored her pleas and united to defeat the Government again.

The Bill is already set to return to the Commons on Wednesday, when the Prime Minister is expected to use his big majority in the elected House to overturn the Lords defeats in the run-up to Brexit day on January 31.

The Prime Minister’s official spokesman told reporters: “We are disappointed that the Lords has chosen to amend the Withdrawal Agreement Bill after the Commons passed it unamended.

“We will seek to overturn this amendment as the Bill returns to the Commons.”