Downing Street’s secrecy over its Brexit proposals has caused a fresh rupture in the negotiations in Brussels, a leaked email reveals, as EU officials warned that the talks are “going backwards”.

The row was sparked by a British demand that the EU’s negotiating team treat a long-awaited cache of documents outlining the UK’s latest ideas as “Her Majesty’s government property”.

Whitehall told the European commission team that the three “confidential” papers should not be distributed to Brexit delegates representing the EU’s 27 other member states.

Sources in Brussels said that in response the point was made forcefully to the British negotiating team that all proposals would need to be made available for the EU’s capitals to analyse for talks to progress.

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With just six weeks to go until 31 October when the UK is due to leave the EU, there is despair in Brussels at the state of the talks, with the latest ideas seen as “more of the same” from Downing Street.

The Brexit secretary, Stephen Barclay, was unable to offer any positive comments about progress in the talks during a visit to Brussels, beyond noting that his one-hour meeting on Friday with the EU’s chief negotiator, Michel Barnier, had lasted 20 minutes longer than expected.

His trip to Brussels coincided with the end of the 30-day “blistering timetable” to break the Brexit deadlock, declared by Boris Johnson when he met Angela Merkel in Berlin.

“The meeting actually overran, which I think signals the fact that we were getting into the detail and we’ll have further discussions next week,” Barclay said of his talks with the EU negotiator.

Asked about claims from the Irish government that the two sides are far apart in their negotiating positions, Barclay added: “There is still a lot of work to do but there is a common purpose to secure a deal.”

A statement from the European commission described the British contribution in the latest talks as “a first set of concepts, principles and ideas”. The commission insisted it was “essential that there is a fully workable and legally operational solution included in the withdrawal agreement”.

After updating the European council president, Donald Tusk, on the latest developments, Barnier offered a downbeat assessment of the state of play.

“Very clearly, we are always ready to examine, on an objective basis, any proposals,” he said. “But these proposals of the UK must reach all the objectives of the backstop – protect peace in Ireland, protect the all-Ireland economy and protect the consumers and businesses in the EU single market.”

Barnier continued: “What I can say after my meeting – a very cordial meeting with Steve Barclay and his team – lots of work has to be done in the next few days. The Brexit is a school of patience, but we are still ready to reach an agreement.”

The Dutch prime minster, Mark Rutte, suggested during a press conference in The Hague that he had yet to see “real specific proposals”. Tusk is meeting Johnson and the Irish taoiseach, Leo Varadkar, on Monday at the UN general assembly in New York.

During a visit to a refurbished runway in Knock, west Ireland, Varadkar was given holy water by a priest to “help” him during his meeting with Johnson in New York. “Do I throw it over him?” Varadkar said.

The three papers submitted ahead of the latest talks by the UK fleshed out issues already broached by Johnson’s chief negotiator, David Frost, in recent weeks. Many of the ideas had been previously rejected at various points in the last two years of talks. “They confirmed there would be a customs border on the island of Ireland – it is a horrible mess,” said a source.

One official suggested the proposals may have been submitted purely to offer some evidence to the supreme court that there was a negotiation going on in Brussels and that Johnson is not heading for a no-deal Brexit. The court is expected to come back with its ruling early next week on whether the prime minister misled the Queen on his motivation for suspending parliament.

The ideas raised by the UK include the use of technology and trusted traders’ schemes to facilitate customs checks away from the Irish border and the joint surveillance of the market in manufactured goods to ensure substandard goods do not enter the single market.

The one area of convergence is on the need for an all-Ireland sanitary and phytosanitary (SPS) or agrifood zone. The final UK paper opens discussions on the scope of such a zone.

Explaining to the EU27 the failure to provide copies of the papers to the member states’ representatives, the commission’s Brexit taskforce wrote in an email that they had been blocked from doing so.

“The UK labelled the documents as HMG property and requested us not to do any onward disclosure,” the taskforce wrote, according to an email seen by the Guardian. “We intend to discuss working methods with the UK in terms of transparency and sharing information.”

Speaking to BBC Radio 4’s Today programme, the Irish deputy prime minister, Simon Coveney, said the gap between the two negotiating positions was wide and there was no basis for an agreement.