The European parliament has said it would veto Boris Johnson’s Brexit proposals, warning that they are not “even remotely” acceptable as a solution to the Irish border problem.

It comes as the Irish government warned that it “cannot possibly” support the plan in its current form, and encouraged the UK to come back with something “fit for purpose”; while the European Commission said it was down to the UK to fix a number of “problematic points”.

Speaking after a meeting of the parliament’s Brexit steering group, coordinator Guy Verhofstadt said the plans were “mainly a repackaging of the bad ideas that have already been floated in the past”.

In a joint statement released on Thursday afternoon, the cross-party committee of MEPs charged with setting parliament policy on negotiations – including the use of its veto – warned that it has “grave concerns about the UK proposal, as tabled”.

“Safeguarding peace and stability on the island of Ireland, protection of citizens and EU’s legal order has to be the main focus of any deal. The UK proposals do not match even remotely what was agreed as a sufficient compromise in the backstop,” the committee said.

“The Brexit steering group does not find these last-minute proposals of the UK government of 2 October, in their current form, represent a basis for an agreement to which the European parliament could give consent. The proposals do not address the real issues that need to be resolved, namely the all-island economy, the full respect of the Good Friday Agreement, and the integrity of the single market.”

The parliament has three main concerns with the proposals: it says plans for customs checks represent “a serious risk to the peace process” in Ireland; that the half-finished nature of the plans “do not provide the necessary certainty”; and that the veto given to Stormont “makes an agreement contingent, uncertain, provisional” and subject to a unilateral decision.

“The question is: is this a serious compromise? And we have serious doubts about that, certainly after the leak of a paper, a document, by Downing Street to the Tory MPs to blame the European Union directly,” Mr Verhofstadt told Channel 4 News.

“If there is a Tory document saying that they have to blame the European Union then it’s obvious that that is the purpose ... The backstop is in fact a safeguard that is a type of insurance that you never hope to use. That’s a backstop. And this is quite the opposite, what is proposed. It’s temporary, so it’s not for a long period. It’s depending on the consent of an assembly in Northern Ireland that, for three years, has not been seated, was never in place. And there are serious doubts that it will be in place in the coming years.”

Speaking in Ireland’s parliament on Thursday, the country’s deputy prime minister Simon Coveney echoed EU concerns about the customs checks and built-in veto for the Northern Ireland Assembly.

EU says ball is still in the UK's court on getting Brexit deal done

“We cannot support any proposal that suggests that one party or indeed a minority in Northern Ireland could make the decision for the majority in terms of how these proposals would be implemented in the future,” he said.

“That is not consistent with the Good Friday Agreement. It is not something we could possibly support as part of any final deal.”

He added that there were “legal and technical” problems with the plan, stating: “Despite this paper saying they want to avoid customs checks, they do raise the prospect of customs checks somewhere, not just in premises and businesses, and we think that’s going to be a real problem.”

Mr Coveney expressed hope that the plan could be developed into something that was “fit for purpose” and be a starting point for negotiations. Leo Varadkar later told reporters at a press conference that having two customs zones on the island of Ireland was “going to create a real difficulty that’s going to be very hard to reconcile”.

The UK proposals do not match even remotely what was agreed as a sufficient compromise in the backstop European Parliament Brexit Steering Group

Back in Brussels, a spokesperson for the European Commission warned that it was down to the UK to fix the “problematic” aspects of the proposals.

Asked whether Brexit secretary Stephen Barclay was right to say that the ball was “in the EU’s court” following the release of the policy on Wednesday, a spokesperson for the European Commission said the EU would not be left “holding the bag” and that it was the UK that needed to act.

“We would disagree.” she told reporters in Brussels. “There are, as we have said, problematic points in the United Kingdom’s proposal and further work is needed – but that work needs to be done by the United Kingdom and not the other way around.

“We would remind you that it’s the UK leaving the European Union and not the EU leaving the UK.

“We are doing everything in our power to ensure that exit is on an orderly basis and we are willing to engage constructively with our counterparts. But we are not going to be the ones left holding the bag, the ball, or any other kind of object.”

Boris Johnson defends the proposals in the House of Commons (AP)

European Council president Donald Tusk said on Thursday: “My message to taoiseach Leo Varadkar: We stand fully behind Ireland. My message to prime minister Boris Johnson: We remain open but still unconvinced.”

An initial polite but firm response from Brussels to the plans on Wednesday evening had been interpreted ambiguously back in the UK, with EU officials saying they would study the plans before commenting in detail.

But reaction behind the scenes hardened on Wednesday. One senior EU official said the UK proposals “can’t fly” and that plans to give the Northern Ireland assembly a veto over the plan were not acceptable.

Jean-Claude Juncker, the European Commission president, is expected to call Irish premier Leo Varadkar on Thursday afternoon to discuss the proposals. A spokesperson for Mr Juncker said he would “reiterate the EU’s continued unity and solidarity behind Ireland”.

Both Ireland and Brussels have dismissed reports in the UK media that Ireland is under pressure to accept the proposals. The country’s European affairs minister Helen McEntee said: “Our EU partners have stood beside us for the last three-and-a-half years, and that has not changed. We are not coming under pressure to change those key objectives.”

She added that the proposals were “a basis for discussions” but that there “are obvious concerns”.

Under the British plan, Northern Ireland would stay aligned with the EU single market regulations for goods, but stay in the UK customs zone. The result would be customs checks on products moving between the Republic of Ireland and Northern Ireland, and regulatory checks on products moving between Great Britain and Northern Ireland. The UK government says the checks could be done away from the border, though has provided little detail on how – with critics warning the sites would be customs centres in all but name.

Simon Coveney said Ireland could not agree to the plans (PA)

The Northern Ireland assembly and executive would also have to vote to keep the plan going every four years, effectively constituting a veto.

The proposal has been received very poorly in Northern Ireland, where only the DUP has welcomed it out of the territory’s main political parties. Business groups also condemned the plan, with a spokesperson for Manufacturing NI saying it would be “worse” than a no-deal Brexit and “decimate” entire industries.

In the Commons, Boris Johnson indicated that he might be open to making further concessions to Brussels if it helped unblock talks. But he also faced a torrent of criticism that his plan lacked support in Northern Ireland and would break the law by imposing new customs checks.

Challenged to name a single business that backed the blueprint, the prime minister was only able to say that companies badly wanted an agreement of some sort.

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Hilary Benn, the chair of the Commons Brexit Committee, protested that the proposals put the Good Friday Agreement at risk.

He pointed out that the withdrawal act passed last year bars any new “checks and controls” in Ireland – yet Mr Johnson had announced “there will be customs checks in Northern Ireland”, albeit not at the border.

And Sylvia Hermon, independent MP for North Down, said: “The prime minister’s proposals prove quite clearly that he does not understand Northern Ireland.

“While the prime minister is perfectly happy, it seems, to dance to the tune of his friends in the Democratic Unionist Party, he forgets or chooses to ignore the fact that the DUP does not represent the majority of people in Northern Ireland.”

Lady Hermon added: “The majority of people in Northern Ireland will be extremely concerned by the proposals that he has tabled yesterday, which introduce two borders.”