Ireland's EU Commissioner Phil Hogan has launched a withering attack on eurosceptic hardliners in the British government.
Speaking in Brussels, Mr Hogan accused British politicians of deriding facts and details, and of adopting a "bullying" approach to the Brexit negotiations.
Mr Hogan said: "What becomes more obvious day-by-day is that the Brexiteers are hooked on brinkmanship - and have been since the beginning.
"Unfortunately, their only approach is the tough-guy approach.
"No matter what Brussels says or does, no matter what business in the EU says or does, no matter how many companies announce plans to move workers from the UK to new EU headquarters, the hardliners cannot get out of their head the idea that if they bully their way towards the wire, the [EU's] nerve will crack.
"They cannot get it into their head that this is not how the European Union works.
"Unfortunately, we are now so close to the cliff edge of a hard Brexit that we can see the drop right in front of our feet."
Mr Hogan also criticised what he called the British government's lack of workable solutions on the Irish border.
"It is painfully clear that the UK government is not going to propose workable solutions for the benefit of the island of Ireland," he said.
"Indeed, the low priority afforded to Northern Ireland by London is disheartening, to say the least.
"We hear regularly about the need for 'frictionless borders' but the only policy positions outlined thus far would achieve the exact opposite."