The EU "intends to teach" Britain "what leaving the single market means", the trading bloc's chief negotiator has said.
Speaking in Italy over the weekend, Michel Barnier said Brexit should be "an educational process" for the country.
"There are extremely serious consequences of leaving the single market and it hasn't been explained to the British people," he said. "We intend to teach people… what leaving the single market means."
Barnier also indicated he would not back down at this stage in the talks.
"I have a state of mind - not aggressive... but I'm not naive," he said.
Barnier and Brexit secretary David Davis are no longer making any efforts to hide their mutual animosity.
Yesterday Davis told Andrew Marr of his growing frustrations at the way talks have been conducted so far, slamming the decision not to open negotiations up to discuss trade until the divorce bill has been agreed.
He said: "That's the point about the Europeans. They won't talk about the future. They'll only talk about so-called divorce proceedings."
"Of course [Barnier] wants to put pressure on us, which is why the stance this week in the press conference - bluntly, I think it looked a bit silly, because there plainly were things that we achieved," he said.