Conservative former Cabinet minister Lord Heseltine has been dramatically sacked as a government adviser after rebelling over Brexit.
The Tory grandee backed demands for a 'meaningful' vote on the final Brexit deal after warning quitting the European Union was the 'most momentous peacetime decision of our time'.
He was later told Prime Minister Theresa May was firing him from his roles advising the Government on a number of areas, including its industrial strategy.
One of his roles was as an advisor to the Secretary of State for Communities and Local Growth.
Peers backed his controversial cross party amendment by a majority of 98, voting 366 to 268 in favour, prompting fury from Brexit secretary David Davis.
Lord Heseltine led the fight for the amendment today as he warned the final Brexit deal was 'totally unpredictable' and the referendum mandate was not unlimited.
But Brexit supporters warned the amendment, which demands Parliament has the right to send Mrs May back to Brussels for a better deal, would damage the Government's ability to negotiate.
The Brexit Bill is due to clear the Lords late tonight after marathon debates on the 137-word Bill.
Mrs May will demand MPs overturn any changes to the Bill when it returns to the Commons on Monday.
The Prime Minister will hope her decisive action will discourage potential Tory rebels in the Commons.
The legislation, which hands the Prime Minister power to start official Brexit talks, is expected to be law by the middle of next week regardless of defeat tonight.
After the vote, Mr Davis 'It is disappointing that the House of Lords has chosen to make further changes to a Bill that the Commons passed without amendment.
'It has a straightforward purpose - to enact the referendum result and allow the Government to get on with negotiating a new partnership with the EU.
The Lords is finishing its scrutiny on the Brexit Bill today with its report and third reading stages.
Today's debate will see detailed discussion on a new set of amendments before a final vote on the principle of the legislation, which is about triggering Article 50.
Because the Government has already been defeated, on EU nationals, the BIll is already headed back to the Commons for a further debate.
This is due to happen on Monday and MPs will spend about an hour discussing the Lords amendments.
If they reject them as planned, the Bill will 'ping pong' back to the Lords.
Peers are expected to then back down, meaning the legislation can be sent to the Queen for Royal Assent, making it law.
In his speech, Lord Heseltine said he backed triggering Article 50 in response to the Brexit referendum.
And he praised the Prime Minister's handling of the post referendum period and the formation of her Government.
But of the referendum result, Lord Heseltine said: 'I do not accept that the mandate runs for all time and in all circumstances.
He went on: 'We now face a protracted period of negotiation. No-one has the first idea of what will emerge.
'No-one can even tell us what governments in Europe will be there to conclude whatever deal emerges.
The peer understood it would take 1,600 regulations to 'unravel over 40 years of closer union'.
He said: 'Everyone in this House knows that we now face the most momentous peacetime decision of our time.
'And this amendment secures in law the Government's commitment ... to ensure that Parliament is the ultimate custodian of our national sovereignty.
Leading Brexiteer Lord Lawson admitted the prospects of getting a deal within the two year Article 50 process were slim.
Holding a second referendum on the final Brexit deal would add to the nation's divisions and 'deepen the bitterness', the Archbishop of Canterbury has warned.
The Most Rev Justin Welby said last June's vote on leaving the EU has exposed deep splits within society and stressed the need to find 'a level of national reconciliation'.
The former Chancellor said: 'No agreement is by far and away the most likely outcome.
Moving the cross party amendment Lord Pannick - who represented Gina Miller in the Supreme Court case that forced the Bill to be brought - said: 'The purpose of this amendment is very simple.
He said the Prime Minister's commitment to such a vote should be written into the Bill 'no ifs and no buts'.
The Labour-led amendment, tabled with Lib Dem and crossbench support, also required the approval of both Houses if the Prime Minister decided that the UK should leave the EU without agreement on the terms.
'It must be for Parliament to decide whether to prefer no deal or the deal offered by the EU,' Lord Pannick said.
Former Conservative leader Lord Howard said MPs would get a say on the deal no matter what course of action the Government took.
'The Commons will not only have its say, the Commons will have its way,' said Lord Howard.
Mrs May's spokesman made clear there had been no change on the Prime Minister's position on the Brexit bill.
He said: 'She's been clear that she wants an unamended bill to pass. This is a simple bill with one purpose, to give the Government the power to trigger Article 50, that's where we are.
Launching the demand for a second referendum, Lord Newby, Liberal Democrat leader in the Lords said: 'It would require any Brexit deal to be put to the people to approve or reject.
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.
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'.
Lord Newby's amendment was heavily defeated by peers, ending prospects of a second referendum being added to the Bill.
The Archbishop said instead politicians must 'find a level of national reconciliation'.
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'.
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.
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'.
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.