Donald Tusk, the president of the European council, has rejected Boris Johnson’s demands for an alternative to the backstop.
Tusk defended the measure and warned that those seeking to replace it would risk a return to a hard border on the island of Ireland.
He tweeted: “The backstop is an insurance to avoid a hard border on the island of Ireland unless and until an alternative is found.
“Those against the backstop and not proposing realistic alternatives in fact support reestablishing a border. Even if they do not admit it.”
Johnson had written to Tusk outlining his opposition to what he called the “anti-democratic” Northern Ireland backstop.
In the letter, Johnson said while he wants the UK to leave the EU with a deal, he could not support any withdrawal agreement that “locks the UK, potentially indefinitely, into an international treaty which will bind us into a customs union and which applies large areas of single market legislation in Northern Ireland”.
As an alternative to the backstop, the prime minister said the UK would agree to a “legally binding commitment” not to put in place infrastructure, checks or controls at the border with Ireland and would hope the EU did the same.
The backstop should be replaced with a commitment to put in place “alternative arrangements”, as far as possible before the end of the transition period, as part of the future relationship between the UK and EU.
In a note circulated to diplomats from the EU27, officials describe points made by Boris Johnson as “misleading” and “incorrect”.
The EU document takes issue with Johnson’s claims about the Good Friday Agreement and the Irish border.
The briefing note said the Withdrawal Agreement “fully respects the Good Friday (Belfast) Agreement, the constitutional status of Northern Ireland and the territorial integrity of the United Kingdom”.
It was “incorrect to state that the people of Northern Ireland have no influence over the legislation that would apply to them” and the note highlights “specific governance arrangements” which could allow the UK and the people of Northern Ireland to express their views and to influence the shaping of the decisions.
The note continues: “The letter’s suggestion that two separate legal, political, economic, and monetary jurisdictions already exist on the island and can be managed with an open border is misleading.
“EU law provides the common framework needed to enable frictionless trade between Member States today. Without this common framework, checks and controls become necessary to protect consumers’ health, the integrity of the Single Market and Ireland’s place in it.”
A European Commission spokeswoman Natasha Bertaud welcomed the government’s attempt to engage with the EU, but echoed Tusk in dismissing the lack of substance in the proposal.
She said: “We welcome the UK government’s engagement and continued commitment to an orderly withdrawal. We firmly believe this is in the best interests of both the EU and the UK.
“However, we also note that the letter does not provide a legal operational solution to prevent the return of a hard border on the island of Ireland.
“It does not set out what any alternative arrangements could be and in fact it recognises that there is no guarantee that such arrangements will be in place by the end of the transitional period.
“Otherwise, as we have said on many occasions, we do stand ready to work constructively with the UK and within our mandate.”
Best for Britain supporter Virendra Sharma MP has reacted by saying that it was clear the only way to protect Ireland is to remain in the European Union.
He said: “This was always going to be the EU’s reaction to an inward-facing letter sent out by the prime minister.
“As Donald Tusk makes plain, actions are more powerful than words and if you want to scrap the backstop without a solution being in place then you’re not doing anything to prevent the return of a hard border.
“Even senior US politicians such as Chuck Schumer and Nancy Pelosi have been voicing their determination to block a US trade deal if the prime minister doesn’t resolve this issue.
“It’s clear that the only democratically viable solution that protects these communities would be to retain our current membership of the EU.”