The Government has suffered a heavy defeat in the Lords over giving MPs a "meaningful vote" on the final Brexit deal.
Voting was 354 to 235, majority 119, for an amendment to the European Union (Withdrawal) Bill tabled by Tory former minister Viscount Hailsham.
It was worded along the lines of the agreement Tory former attorney general Dominic Grieve thought he had reached with the Government last week.
The vote kicks the controversial issue back to the Commons in a further round of parliamentary "ping pong", with MPs expected to debate it on Wednesday.
Lord Hailsham said the Government had failed to deliver its promise to provide a "meaningful vote" on the Brexit deal and it was up to peers to insist on it to give MPs another chance to debate the issue.
But Lords' leader Baroness Evans of Bowes Park said the amendment had "flaws" and insisted the Government had come back with a "fair, practical and constitutionally sound offer" to meet the demands of peers and MPs.
The vote, at the end of a bad-tempered debate in the Lords, came after the Prime Minister warned that Parliament must not be able to "overturn the will of the British people".