They are rallying around an amendment giving the House of Commons power to send the government back to the negotiating table with Brussels if lawmakers don't like the terms of the Brexit deal struck with the EU.
The disagreement centres on whether the government agreed to consider a specific clause of the rebel proposal that would hand parliament control of the Brexit process if ministers are unable to strike an exit deal by February 15, 2019.
He said the United Kingdom should "re-engage with our European and worldwide friends to talk about how to achieve the aims that we share for the future in ways that respect individual countries' interests and sovereignty", taking into account concerns expressed in other EU countries since the Brexit vote about the bloc's direction. Several pro-EU Conservative lawmakers said they would join the opposition in voting against the government.
He claimed the PM had delayed the transition from December 2020 until December 2021, something Mrs May dismissed as "quite wrong" as she said the backstop arrangement would come into force if it is not possible to put future customs arrangement in place by January 1 2021.
Furious Scots walk out of United Kingdom parliament over Brexit
Mrs May met pro-EU Tories in her private room in the Commons moments before a crucial vote to hear their demands for a truly meaningful vote on the final exit deal.
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.
Potential rebels fell into line after Mr Buckland said ministers were ready to "engage positively" with their concerns before the Bill returns to the Upper House next Monday.
It was always going to be a tough couple of days in the House of Commons for Theresa May's government and her Brexit strategy.More news: Garmin Vivoactive 3 gets onboard storage for music
The amendment, which would push the government towards adopting a Norway-style deal with Brussels, was voted down by 327 votes to 126, a majority of 201.
He later claimed Mr Johnson "inhabited a parallel universe" in which the referendum result is not respected "unless you want friction at the borders and disruption of the economy". The Sun reports that Brexiteers are not allowing any more Government amendments.
However, May is anxious about the prospect of a rebellion by pro-EU Conservative MPs who are determined to retain as numerous changes as possible. This means MPs and Lords could tell May to go back to negotiating table and get something better.
But while that vote seemed assured, tensions over Britain's departure from the European Union boiled over in parliament, where lawmakers from the Scottish National Party walked out in the middle of questions to the prime minister in protest at what their leader said was Scotland being ignored in the Brexit debate. This is where Conservative rebels like Nicky Morgan, Anna Soubry and Ken Clark are expected to make their biggest move on customs. It's a significant weakening of the Lords amendment, and doesn't appear to give lawmakers much sway at all.More news: United Nations seeks urgent ceasefire to stop UAE assault on Yemeni port
It also imperils the now invisible border between the U.K.'s Northern Ireland and the Republic of Ireland, an European Union member.
May said the government would amend the bill to address legislators' concerns, but warned that "I can not countenance Parliament being able to overturn the will of the British people".More news: Uber wants to patent technology to detect drunk riders