"When we published our plans in June on a UK-wide customs backstop, we were absolutely clear that the arrangement would be temporary, and only in place until our future economic relationship is ready", the spokeswoman said.
The issue of the Northern Ireland "backstop", the contingency plan in place to avoid a hard border, is thought to have been the main point of discussion at the meeting.
Simon Coveney, who is also Ireland's foreign minister, directly contradicted UK Brexit Secretary Dominic Raab's stance on a key part of the UK's withdrawal agreement.
Numerous problems are now being solved on a step by step basis "but there are, of course" several big issues which we really need to get to grips with, ' the prime minister said.
Parliament has demanded a "meaningful vote" on the divorce deal, and the Prime Minister's slim majority - plus her reliance on votes from her unionist allies in Northern Ireland - means she could fall at the first hurdle.
The experts behind the report, produced by UCL's Constitution Unit, acknowledged the prospect of a so-called People's Vote is contentious but said it would be perfectly achievable given the political will.
This divergence with Britain would require some form of checks on goods travelling across the Irish Sea. Some of May's ministers have urged a time limit on that.
The prime minister briefed ministers on negotiations yesterday amid speculation that the government is moving closer to a deal with Brussels.
The Prime Minister is likely to face a major backlash from Eurosceptics within her party over the plans, with Leave-backing Cabinet members expected to resist such concessions.
Blasting the proposed deal, she said: "Trade from Great Britain into Northern Ireland would be in danger of restriction".
Oliver Robbins and May will try to reconcile this contradiction by persuading the rest of the European Union to sign up in the separate political declaration that a future commercial relationship between the United Kingdom and the European Union will deliver "frictionless, tariff-free trade" between United Kingdom and EU.
Sir John said that their behaviour was even worse than that of the Eurosceptics he famously dubbed "bastards" when he was in No 10 in the 1990s.