Brexit negotiations have begun to dramatically sour after months of deadlock, with exasperated EU officials tearing into Britain’s “fantasy” negotiating strategy and warning that Theresa May’s latest customs plan would ruin any chance of progress.

This week’s latest meetings are understood to have produced no progress on the core issues of the Northern Ireland border and customs, with last year’s business-like start to discussions having given way to bitter behind-the-scenes briefings.

One senior EU official said the UK still lacked negotiating positions on a wide variety of issues and that in others it was “chasing the fantasy of denying the consequences of Brexit in a given policy area”.

Another Brussels official close to talks told The Independent they had been warned internally that there would probably be no progress by the June meeting of the European Council – which would throw off the timetable and raise the risk of a disastrous “no deal”.

News that Theresa May wants to align the whole UK with the customs union and single market on a time-limited basis until 2023 as a backstop to solve the Irish border issue was particularly poorly received in Brussels.

The Prime Minister is due to actually announce the new policy in the comings weeks, but people familiar with the talks confirmed it had already been raised by UK negotiators. The European Commission’s negotiators have already rejected the plan before its public announcement, as first revealed by The Independent earlier this week.

“The regulatory alignment option is not available on the all-UK basis because it would amount to selective participation on the single market,” the senior EU official said, adding that the backstop “cannot be time limited”.

It is incumbent on the UK to take the responsibility for its own decision

Senior EU official

“A backstop that would be strictly time limited would defeat the purpose of a backstop,” they said, before making clear that the Prime Minister’s plan for a UK-wide backstop would have to be withdrawn if progress is to be made at the June European summit.

As well as the main issues of customs and the Irish border, side issues like the European arrest warrant and the Galileo satellite system have made little progress since March too. EU negotiators complain that the British side “do not understand” that Britain will not be able to use the European arrest warrant after Brexit, with Theresa May again having pledged to stay in the system just three months ago.

“There are member states that simply cannot extradite their own nationals to a non-member of the EU. This is a constraint that unfortunately will apply once the UK is outside,” the senior official said.

“The European arrest warrant is simply not available. I don’t think you can expect member states to change their constitutions in order to continue extraditing their nationals to the UK.

“These are not bureaucratic issues. We are talking here about the lives and liberty of citizens. This is not something that can easily be done.”

Brussels says the best the UK can hope for is to conclude a separate extradition treaty with the EU, as well as bilateral agreements on procedures like intelligence sharing.

The row over Galileo has also been the subject of briefing and counter-briefing by the two sides. British sources briefed newspapers this week that they would demand the UK’s £1bn investment in the project back if British companies were locked out of the project. But EU sources disputed whether this stand had actually been made, describing the claim as “spin”.  

The EU says British demands to retain the same access to Galileo as a member state are unreasonable. Though officials say Britain could potentially still use the system, they do not want to give British defence firms the right to build or run parts of it because they say that would effectively give the UK, a third country, the power to turn off the EU system for member states. 

Officials also pointed out that the UK itself had signed off the security rules restricting non-EU countries from running parts of system, as one of the 28 European Council members, before it knew it was going to leave.

David Davis, the Brexit Secretary, who is travelling to Europe to drum up support for the UK to keep access to the satellite system, said: “Today we set out more detail on how we think the UK, as a third country, can continue to cooperate with the EU on security and keep our people safe and prosperous. As I travel around member states I hear how much our partners value the UK commitment to the EU’s security.

“A relationship based solely on existing third country precedents, as some seem to be suggesting, would lead to a substantial and avoidable reduction in our shared security capability. Our citizens depend on this, let’s not let them down.”

The senior EU official said they shared the UK’s concerns but that “this is a consequence on the UK position and it is incumbent on the UK to take the responsibility for its own decision”.

Brussels has also dismissed the UK’s entire philosophy towards the future trade relationship, which the UK wants to be on the basis of the mutual recognition of standards. Officials say mutual recognition is not possible outside the single market, because it would amount to asking “the EU to trust the UK more, with less guarantees, than they trust each other”.

Michel Barnier, the EU’s chief negotiator, has said Theresa May’s red lines mean Britain can only get a free trade agreement similar to the ones the EU has with Canada and South Korea, but the UK said today that this “shallow level of cooperation” was “inconsistent with our ambition”, which would require “a more formal and deeper institutional structure”.