EU tells UK to stop with Brexit 'fantasies'

The official also said that the UK will start having to take responsibility for its decision and accept that Brexit will mean a looser relationship with the EU.

"The UK thinks everything needs to change on the EU side, so everything can stay the same on the UK side," the official quipped.

The official warned substantive progress on the border between Northern Ireland and the Republic of Ireland by the June meeting of EU leaders remains elusive.

EU chief negotiator Michel Barnier said earlier that progress needs to be made on guaranteeing a unique solution by June so that a hard border can be avoided.

The UK agreed in December to a "backstop", that would align Northern Ireland's regulations with that of the EU's.

But the London government has been struggling to come up with concrete solutions, as British prime minister Theresa May's government is dependent for her majority on hardline unionist Northern Irish allies opposed to barriers between Northern Ireland and the British mainland.

May suggested making the backstop time-limited.

However, the EU official dismissed that, arguing that a deadline for ending the backstop would make it pointless - just delaying the possible introduction of a hard border which could risk decades of peace process in the volatile region.

"We need to have the recognition that the backstop has to be Northern Ireland-specific," the official said.

UK negotiators also told the EU that London wants to solve the Irish border issue as part of the overarching EU-UK future relationship deal, but the EU has said - again - that would not be possible.

The EU is concerned that this way London wants to couple avoiding the hard border with a bid to secure better "backdoor" access for the rest of the UK to the bloc's single market.

The official said the UK has promised new ideas within the next two weeks, but sounded concerned about possible progress.

"I have to say on the basis of this week's discussions, I am a bit concerned because the pre-condition for fruitful discussions has to be that the UK accepts the consequences of its own choices," the official added.

More obstacles

The blunt warning comes as the withdrawal agreement needs to legally finalised by October for it to be ratified by the UK and the European Parliament before Brexit-day next March.

Solving the Irish border issue is a prerequisite for finalising the withdrawal deal, as EU officials warn that without the agreement there would be no transition time for the UK planned until 2020.

Other issues of separation also presented difficult obstacles during the three days of talks.

The UK rejected the EU's offer for a free trade deal at the core of the future relationship, arguing it does not provide a deep enough relationship.

However, the EU is reluctant to give more as that would entail participating in the single market, which would require a common judicial guarantee, a court, namely a role for the European Court of Justice's (ECJ), which the UK has rejected.

The UK also wants to continue participating in the EU's criminal extradition system and the high-security parts of the Galileo satellite programme.

These were also unacceptable to the EU, because the UK does not want to agree to the ECJ's legal supervision.

The official emphasised that the the EU's cooperation is based on common rules with a common legal oversight and the UK cannot expect the same treatment without agreeing to the legal remedies.

The official also told reporters that British negotiators said they would use their EU membership until Brexit to to try to change the rules for access to non-member states in the EU budget.