Lawmakers debated yesterday whether Britain should stay in a customs union with the EU after Brexit, as supporters reported growing parliamentary opposition to the government's plans for future ties with the bloc.
The Conservative government has repeatedly ruled out continued membership of a customs union after Britain leaves the European Union in March 2019, arguing that it would limit their ability to strike trade deals with other countries.
But pro-European MPs report increasing support for the idea, which is backed by Britain's biggest business group the CBI, as a way of preserving trade ties with the bloc and avoiding a hard customs border between Northern Ireland and the Republic of Ireland.
Backbench MPs in the lower House of Commons put forward a motion yesterday calling for "the establishment of an effective customs union" to be included in London's Brexit negotiating objectives.
The government is widely expected to ignore the motion, but it will be an indication of looming battles ahead.
Brussels has indicated it is open to Britain changing its position even as the clock ticks down on the negotiations, with London aiming for broad agreement on the future trading relationship by October.
And the government is facing a series of parliamentary showdowns on the customs union.
MPs will hold a binding vote next month on an amendment tabled by the unelected upper House of Lords to the EU (Withdrawal) Bill, which sets the legal framework for Brexit, although ministers have played down its significance.
They are more worried about amendments tabled to its long-delayed trade and customs bills, demanding ministers take "all necessary steps" to allow Britain to continue in a customs union.
The main opposition Labour party backs this position with some conditions, while the trade bill amendment is signed by 10 members of May's Conservative party -- with at least another three said to be supportive.
Some MPs believe a show of support for a customs union would also open the door for parliament to back Britain staying in the EU's single market, another thing May has ruled out.