The Government is facing fresh challenges to its Brexit Bill in the Lords as peers piled pressure on Theresa May's timetable for leaving the EU.
Ministers look likely to suffer another defeat on the legislation later today as the Opposition pushes for a "meaningful" vote on the final divorce deal.
But first came a call from the Liberal Democrats for the outcome of Brexit negotiations to be put to the people in a referendum.
The European Union (Notification of Withdrawal) Bill is set to clear the Lords late tonight but will have to go back to the Commons after last week's heavy defeat over the rights of EU nationals already living in the UK to remain.
Former Tory leader Lord Hague has urged the Prime Minister to call an early general election to avoid further parliamentary stand-offs over Brexit.
Opening report stage debate on the Bill in a packed chamber, Lord Newby, Liberal Democrat leader in the Lords, called for the people to be given a final say on the Brexit deal.
"This is a very straightforward amendment," he told peers. "It would require any Brexit deal to be put to the people to approve or reject.
"It's based on the principle that having asked the people whether they wished to initiate the Brexit process, only the people should take the final decision."
Lord Newby denied this amounted to "sidelining" Parliament and warned of "corrosive anger" if MPs and peers were to take the final decision going against the majority view at that time.
He said a second referendum would "hardly impinge" on the Government's timetable for quitting the EU and suggested the question put to voters should be: "Do you prefer the deal done by the Government or to remain within the EU."
Challenged by Tory peers that this would provide no incentive for the EU to give the UK a good deal, Lord Newby said our European partners would negotiate in "good faith" and branded such an "unfriendly" view as "deeply depressing".
Labour former cabinet minister Lord Hain said Leave voters he spoke to during the referendum campaign "were voting against something, they were voting against the European Union, but they were not voting in favour of anything".
He added: "The Leave campaign left the alternative deliberately ambiguous."
Lord Hain went on: "I am not disputing the outcome of June 23. This is not about re-running that referendum. This is about making sure that the democratic process remains democratic. That voters have a final say on the eventual negotiated outcome."
Ex-Liberal Democrat Lord Carlile of Berriew, who now sits as a non-affiliated peer, said at the time of the EU referendum there had been no suggestion from his former party that there would be a further public vote.
He said: "It was envisaged by Liberal Democrats that there would be one referendum."
But his comments led to a dig from the party's former leader Lord Ashdown, who said his "recall of what positions the Liberal Democrats took in the past has not always been entirely accurate".
But Lord Carlile hit back, saying: "He's at his best when he makes points with simplicity. That point was not made with simplicity."
On Lord Ashdown's recollection, Lord Carlile suggested he had been "too busy eating his hat", in a gibe at Lord Ashdown wrongly rejecting the shock election night exit poll in 2015, which predicted a Lib Dem bloodbath and disaster for the Labour Party.
Supporting a second vote, Tory peer Baroness Wheatcroft said: "Although I am not an advocate of government by referendum, in this situation, having started the process with a referendum, it seems to me the only sensible way to bring the process to an end is to put the terms to the public."
Conservative peer Lord Robathan said the first referendum had presented a clear "binary choice" which must be respected.
He said: "People knew what they were voting for - they were voting to leave the EU.
"And, my lords, it is unbecoming and very patronising of people to attribute to the individuals in this nation the reasons for which they voted.
"Personally I voted to stay in 1975, some 40 years later I have experienced the EU and I voted to take back control of this country into the hands of the British people."
Fellow Tory peer Lord Hamilton of Epsom said the prospect of a second referendum would encourage the remaining EU states to offer Britain the "most appalling deal known to man" in the hope it is rejected and the UK stays in the union.