The BBC has been told that political uncertainty in the United Kingdom, and the prospect that Parliament could force a change in United Kingdom customs policy, may be strengthening the EU's resolve not to budge on the issue at the moment.
Even if Britain and the European Union were working toward a British exit from the European Union taking place in March 2019, risks of failure remained as long as outstanding topics such as Ireland were unresolved, he said.
A spokesman for May said that he could not substantiate reports coming out of Wednesday's Brussels meeting that British proposals had been roundly rejected by the EU.
The motion, which has been tabled by 10 select committee chairs including Conservatives Nicky Morgan and Sarah Wollaston, will be non-binding but the debate will increase pressure on the government to keep the customs union option alive following a massive defeat on the issue in the House of Lords on Wednesday.
Either way, it crystallises a crunch point for the Prime Minister between tricky local elections and a looming deadline on a solution to the Irish border issue at June's European Council summit. The EU has rejected their proposals on the Irish question because their proposals were fantasy with no basis in reality or in worldwide law.
While talks will continue over the next three weeks to try to achieve a breakthrough, there are fears that the Irish border question could, once again, prove a roadblock in wider Brexit negotiations when European Union leaders meet again in June.
In what is believed to be the first such case as Britain prepares to leave the European Union next year, five Britons living in the Netherlands and two expat organisations took the government to court in January.
"All of us are anxious about our future rights", said Sarah Parkes from the British in Europe group, urging the Dutch government to grant citizenship to Brits who have lived long-term in the country.
Lord Macpherson, the former top official at the Treasury, said the EU's position was "predictable" because of the backstop solution in the Withdrawal Agreement.
"It's an insult to the British people's intelligence to say they didn't realise that part of Brexit would involve leaving the customs union and the single market".
Both sides have committed to avoiding customs checks and other border impediments that might rekindle violence in the British province of Northern Ireland.
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