The EU has offered to abandon 80% of checks on supermarket goods that enter Northern Ireland from Britain but officials in Brussels conceded they were “preparing for the worst” amid signs Boris Johnson is unlikely to accept the deal.

Maros Sefcovic, the EU’s Brexit commissioner, presented four papers at a press conference on Wednesday evening as he sought to bring an end to the destabilising tussle between the UK and Brussels, saying they were not being presented on a “take it or leave it” basis.

An appeal was made for pragmatism from Johnson but the chances of a compromise appeared low. David Frost, the UK’s Brexit minister, remains insistent that an entirely new protocol should be negotiated that does not have a role for the European court of justice (ECJ) as an arbiter of EU law in Northern Ireland.

A three-week negotiating period is expected for talks over the EU’s new proposals but Brussels is equally determined that it will not renegotiate the fundamentals of the tortuously negotiated protocol which keeps Northern Ireland within the single market, policed by the ECJ, and draws a customs border down the Irish Sea.

One EU official conceded there was a “very big gap” between Frost’s demands and the proposals on the table. “Primarily, it’s a call for the UK to be realistic,” the official said of their offer. “Focus on providing certainty, stability and predictability rather than focus on these high-level constitutional issues.

“We think that renegotiating the protocol would create uncertainty. And that’s the opposite of what we need … There’s a reason why negotiations on the protocol lasted for three and a half years. And we think we’ve reached the only workable solution.”

The EU proposal, described as “a new model” on food and medicines, is a significant concession for Brussels, which had previously called for the UK to align with the bloc’s food and plant health rules to avoid checks between Great Britain and Northern Ireland.

While the EU continues to say checks and controls in the Irish Sea border are necessary to avoid a hard border on the island of Ireland, and represent the Brexit choices made by the British government, officials admitted more clearly than ever before that its implementation had created “unintended consequences” for businesses and consumers. “We believe that his package is significant. It goes far beyond tinkering around the edges,” said one official.

The EU is now proposing a “bespoke Northern Ireland specific solution”. This means checks would be removed on 80% of lines on supermarket shelves, with carefully labelled and sourced British sausages, the product that became emblematic of the row between the two sides, no longer at risk of being prohibited.

In a further concession, trucks carrying mixed loads – for example a lorry bound for a Northern Irish supermarket laden with meat, dairy and confectionery – would only have to provide one health certificate for each journey, rather than one for each product line.

Customs paperwork will also be halved by a more generous definition of goods deemed “not at risk” of entering the EU single market via the Irish border.

In exchange for looser controls, the UK will have to ensure border inspection posts are up and running, and that EU officials have access to real-time data on checks.

These are existing requirements of the protocol and EU officials say they have seen progress on access to databases, having previously accused the UK of foot-dragging.

Some market checks will also be intensified to prevent British goods being smuggled into the EU single market through Northern Ireland. Products for the NI market would have to carry individual labels, rather than labels on pallets.

“We are proposing a different model,” said an EU official. “Fewer checks on the one hand, but more guarantees in terms of governance, more market surveillance and for this reason reinforced monitoring of supply chains will also be essential.”

However, in Westminster there is a concern that the market surveillance and checks on sources of products will be as much of a problem for traders as the status quo. There is also no solution contained within Sefcovic’s proposals to the issue of pets travelling from Northern Ireland to the rest of the UK and back again.

In response to threats to affordability and availability of generic medicines in Northern Ireland, the EU will waive a requirement that medical manufacturers move out of Great Britain into Northern Ireland. Companies supplying the Northern Irish market can continue to have their supply “hub” in Great Britain, a privilege not usually afforded to countries outside the EU single market.

Following criticism that the protocol is “undemocratic”, the Northern Ireland assembly, civil society groups and businesses will be invited to take part in “structured dialogues” with the European Commission on implementing the hundreds of EU laws that apply in the region, although they will not have any decision-making power.

EU officials have long argued it was up to the UK to involve Northern Irish citizens and businesses, but now believe they need to take action to improve transparency of the protocol.