Theresa May's landmark Brexit legislation returns to the House of Commons on Tuesday, with the 15 amendments added to it by the upper House of Lords mostly created to keep closer ties to the European Union and give Parliament more power over the divorce process.
Conservative lawmaker Phillip Lee, who voted to remain in the European Union in Britain's 2016 referendum, resigned as a justice minister so he could vote against the government on a key measure.
Pro-EU Conservatives have signalled they remain ready to rebel on Theresa May's flagship Brexit Bill if she fails to deliver a truly meaningful vote for MPs on the divorce settlement.
Dominic Grieve, the former Attorney General, took up the Lords' meaningful vote clause and ran with it in the Commons.
Rebels said May had assured them the government would accept two parts of Grieve's amendment; and immediately open talks on a third, "part c", which would allow MPs to direct the government, if no deal is reached by February next year.
She is expected to come through the latest round of votes unscathed, with a potentially explosive clash over the customs union on Wednesday already defused by a compromise amendment.
Some of the pro-EU rebels said they had been assured by May that elements proposed by Conservative lawmaker Dominic Grieve would be brought into the European Union withdrawal bill, which will sever ties with the bloc and "copy and paste" its laws. Her mission is clear: to find a way to unite the warring Brexit factions in her party before they derail the government.
In a full statement later posted on his website, Lee said his resignation was a protest against the government's attempts to limit the role of MPs in shaping what sort of Brexit Britain will have.
There was little doubt the government would win on the customs union and single market, which some pro-EU lawmakers say is the only way for Britain to retain economically advantageous close ties with the bloc, with the opposition Labour Party also divided over future relations.
The government said it would produce its revised plan on Thursday. He added: "I understand the difficulties MPs representing constituencies which voted strongly for Leave or Remain have on the EEA amendment".
The pro-EU faction got a boost when junior justice minister Phillip Lee resigned Tuesday, saying he could no longer support the government's "irresponsible" plans for Brexit. They should find an agreement by the end of the week before the bill returns to the House of Lords. The government wants the Commons to reject 14 out of 15 amendments introduced by the Lords which are meant to keep Britain close to the European Union after Brexit. "But if we face the prospect of a "meaningless process" rather than a "meaningful vote", Parliament will be enraged".
Ukip leader Gerard Batten said: "The only "meaningful vote" was the verdict of the people in referendum of June 23 2016".
Grieve had offered his own competing amendment, which rebels in the Conservative Party had shown support for.
"First, we must never do anything that undermines the Government's negotiating position or encourages delays in the negotiations", Mr Davis said.
If the Conservative rebels want to win the battle on parliament's scrutiny and control over the final Brexit deal, they must maintain a united front.