The peers will be debating Article 50 in the House of Lords
Leader of the opposition in the House of Lords, Baroness Smith, said there would be no "extended ping pong" with the Commons over the Article 50 bill.
However, the peers will demand some changes to the legislation which went through the Commons before recess.
Former Labour cabinet minister Lord Hain has also claimed he has a mandate to try to amend the bill.
He is to argue: "Critics say 'what right have I, an unelected peer, to oppose this Bill or even to seek radically to amend it?'
"But I was appointed by my party. And in the referendum, two thirds of Labour electors voted to Remain. That's what I am reflecting, that's my mandate."
Lords are expected to debate the bill for the next two days.
Prime Minister Theresa May has promised to trigger the Article 50 by the end of March.
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