Tensions rise between London and Brussels as May accuses EU officials of issuing threats
EU negotiator says that he will pay 'great attention' to the situation in Ireland
The relationship between Britain and the EU has deteriorated further, heightening concerns about the chances of a deal on Brexit.
British prime minister Theresa May launched a blistering attack on the EU, accusing officials of making threats and trying to interfere in the general election.
Mrs May lashed out at European politicians and officials for plotting to "deliberately affect" the result of next month's poll.
She said bureaucrats had "misrepresented" the British position on Brexit, adding that some of them "do not want these talks to succeed".
She hit back after EU chief Brexit negotiator Michel Barnier told Britain to pay an "incontestable" Brexit divorce bill of up to €100bn or face being taken to court.
Mrs May's comments followed leaks of her factious meeting with Mr Barnier and European Commission President Jean-Claude Juncker last week.
Although she was careful not to accuse anyone by name, her speech was clearly aimed at German Chancellor Angela Merkel, who said last week Britain had "illusions" about the outcome of Brexit, as well as Mr Barnier and Mr Juncker .
Mr Barnier also said yesterday he will "pay great attention to the situation in Ireland".
Despite Mr Barnier's assurances, Ireland's Brexit concerns will not be allayed until a second phase of EU-UK talks, due to begin later this year.
A senior EU official said clarity on customs checks for goods crossing the Border and other trade-related issues would take longer to achieve.
"We will not solve all Ireland-specific issues in the first phase," the official said, "but we want to make a good start."
The official said a deal on the transit of goods across the Border would require "a better understanding of what the future relationship will be with the UK in terms of customs".
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Mr Barnier confirmed talks on a future relationship would only begin after the EU gets assurances on citizens, money and borders, the three priorities agreed by EU leaders in their guidelines last week. He said he hoped that could happen by October or November.
"We shouldn't start this second phase of negotiations, on the scoping [of a future trade deal], on the transitional arrangements, in a climate of mistrust and uncertainty," he said. "The UK must put a great deal of energy and effort into these three issues over the next weeks and months and that will increase the chances of reaching a deal."
The EU published more detailed negotiating texts building on those guidelines yesterday, confirming that there should be no return to a "hard border" on the island of Ireland. The texts go further than the leaders' guidelines on customs controls.
"The Agreement should also address issues arising from Ireland's unique geographic situation, including transit of goods (to and from Ireland via the United Kingdom)," the text says.
The text also explicitly recognises the EU citizenship rights of Northern Irish people holding Irish passports, and the common travel area, which was not mentioned specifically in the guidelines.
Mr Barnier, who will visit Ireland next week, took a tough but conciliatory stance ahead of talks with Britain, promising to remain "cool-headed and solution-oriented".
But he hit back at attempts by the British to wind up a deal on citizens in June.
"Negotiations will be difficult," Mr Barnier said.
"Some have created the illusion that Brexit would have no material impact on our lives, or that negotiations can be concluded quickly and painlessly. This is not the case. We need sound solutions, we need legal precision and this will take time."
The EU wants all citizens that have acquired residency, work, pension or other rights in the UK up to Brexit day to keep those rights for life - including citizens that have now left the country.
EU officials also believe the UK does not own a share of the bloc's assets, which include loans, cash, property and other assets valued at €154bn at the end of 2015.
It implies Britain cannot use those assets to offset its final exit bill, though the matter has not been settled.
The EU also insists that the European Court of Justice has a say over the terms of the EU-UK divorce deal, including citizens' rights, long after Brexit.