Peers look set to inflict a second defeat on the British government's Brexit bill by demanding a "meaningful" vote on the final divorce deal.
Independent crossbencher Lord Pannick QC said Prime Minister Theresa May had accepted the need to give parliament a vote on the terms negotiated.
But she was refusing to include that promise in the European Union (Notification of Withdrawal) Bill going through parliament, which will allow the government to trigger the Article 50 process of leaving the EU.
Moving an amendment to the bill, Lord Pannick, who represented lead claimant Gina Miller in the successful Article 50 legal challenge, said parliament should be required to approve the deal at the end of the negotiating process.
But Tory former leader Lord Howard of Lympne said the change would give the Lords a "statutory veto" on the prime minister's decision.
And Tory former cCabinet minister Lord Forsyth of Drumlean warned of a "hidden agenda" behind the move to reject the expressed will of the people in the EU referendum.
Earlier the government comfortably defeated a Liberal Democrat bid to give voters a final say on the Brexit deal in a referendum.
The move to put the outcome of Brexit negotiations to a referendum was heavily defeated by 336 votes to 131, government majority 205.
