The president of the European Commission has said claims he wants to create a European "superstate" are "total nonsense".
Jean-Claude Juncker said some Britons wrongly saw him as a "stupid, stubborn federalist".
He was responding to a speech about Brexit by UK Foreign Secretary Boris Johnson.
Mr Johnson said the EU wanted to create an "overarching European state" and that integration was deepening.
"British politicians, Labour and Tory, have always found that ambition very difficult," Mr Johnson said.
"It is hard to make it cohere with our particular traditions of independent parliamentary and legal systems that go back centuries."
Asked about the foreign secretary's remarks, Mr Juncker replied: "Some in the British political society are against the truth, pretending that I am a stupid, stubborn federalist, that I am in favour of a European superstate.
"I am strictly against a European superstate. We are not the United States of America, we are the European Union, which is a rich body because we have these 27, or 28, nations.
"The European Union cannot be built against the European nations, so this is total nonsense."
Analysis by BBC Brussels correspondent Adam Fleming
As Boris Johnson spoke, the European Commission president Jean-Claude Juncker was holding a press conference in Brussels, completely by coincidence.
He was in typically jolly mood, joking about the drinks EU leaders order at European summits. But the laughing stopped when a British journalist asked him about the foreign secretary's suggestion that there was a plan to build an EU superstate.
"Total nonsense," said President Juncker, who complained that the British political class always misrepresents him.
But he had just spoken about plans for a bigger EU budget and his dream of a directly-elected president of the EU, which some might say made Boris Johnson's point for him.
The foreign secretary's speech has been noted in Brussels - particularly his reference to organic carrots - but negotiators are waiting for the UK to adopt a formal position about its post-Brexit relationship with the European Union.