BORIS Johnson's Brexit deal has suffered a further defeat in the Lords as peers backed calls to give reassurance to Scotland and Wales on devolution powers.

It means defiant peers are on a collision course with the Commons after inflicting five defeats on the Prime Minister's Brexit deal.

In a mauling for ministers, the Lords has backed two more amendments to the European Union (Withdrawal Agreement) Bill.

This follows three defeats yesterday on the rights of EU workers legally residing in the UK to have physical proof of their right to remain and the power of courts to depart from European Court of Justice rulings.

In the latest reverses today, the Government was heavily defeated 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 a fourth defeat for the Prime Minister in just 24 hours.

READ MORE: Peers defeat Boris Johnson in move to restore child refugee rights

Later, the Government suffered a fifth as peers narrowly backed a move underlining the commitment to the so-called Sewel Convention, which states that the UK Parliament "will not normally" legislate for devolved matters without the consent of the devolved legislature affected.

Voting on this Opposition-led amendment was 239 to 235, majority four.

With Brexit day looming on January 31, the Bill, which was passed with big majorities by MPs, will have to return to the Commons for further scrutiny tomorrow.

The Prime Minister looks certain to overturn all the defeats using his 80-strong majority.

It will then be up to peers to decide whether to prolong the bout of parliamentary ping-pong or bow to the will of the elected House, which seems the most likely.

Labour, Liberal Democrat and independent crossbench peers ignored repeated ministerial warnings not to amend the Bill, insisting their objection was not to stop Brexit but to ensure the legislation was better drafted.

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."