Theresa May is facing a week of fresh parliamentary battles over Brexit as clashes centred on staying in a customs union with the EU continue to dog the Government.
With flagship Brexit legislation vulnerable to further attacks in the Lords, pro-European Tory MPs are set to voice their concerns over withdrawal on Thursday.
Downing Street sources insisted there would be no backsliding over quitting the customs union with Brussels after reports that the Prime Minister was ready to take a softer line.
Though the looming Commons vote on a pro-customs union motion would be a symbolic, non-binding one, it has the potential to deepen Tory wounds on Brexit.
Mrs May is set to face calls from leading Brexiteers Boris Johnson, David Davis and Liam Fox to abandon her preferred form of a customs deal with the EU, according to The Times.
A showdown is expected to come at a meeting of the Cabinet Brexit committee scheduled for Wednesday when the trio will tell the PM that a so-called customs partnership, where the UK would collect EU import tariffs on behalf of Brussels, would be unworkable, the report said.
Former Cabinet minister John Whittingdale told BBC Radio 4's The Westminster Hour that defeats like the one the Government suffered last week in the Lords over the customs union played into the EU's hands.
"Part of the problem is that there are some in the European Union and in the Irish Republic who want to make out that we have to stay in the customs union and will not examine other alternatives.
"And votes like ones in the House of Lords are going to add to the view over there that somehow the British Government might U-turn or go back.
"We need to make it absolutely clear that leaving the customs union is an absolutely fundamental part of Brexit. We then have to find a solution to the Northern Ireland border question."