European Commission president Jean Paul Juncker said British prime minister Theresa May was "on another galaxy" and "deluded" about Brexit after the two parties had dinner last Wednesday at Downing Street, German newspaper Frankfurter Allgemeine Sonntagszeitung (FAS) reports.

A U.K. government spokesperson on Monday said the British government did not recognize the account of the meeting, according to the Reuters news agency.

"As the Prime Minister and Jean-Claude Juncker made clear, this was a constructive meeting ahead of the negotiations formally getting underway," the statement said.

Today's FAZ report on May's disastrous dinner with Juncker - briefed by senior Commission sources - is absolutely damning. — Jeremy Cliffe (@JeremyCliffe) April 30, 2017

European Commission sources leaked information of the dinner to FAS, according to the Telegraph newspaper. The article claims May said she believes the U.K. is not legally obligated to pay anything to the E.U. under existing treaties, despite the body's assertion that Britain would owe up to 50 million GBP to fulfill its obligations to the block upon its exit.

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E.U. representatives also reportedly said May's desire for an early deal on E.U. migrants would not be feasible before June, which was her suggested timeline, and that it would be impossible for the talks to remain confidential.

The article in FAS was published in full only in print, and there is no English language version available.

When E.U. parties suggested the U.K. could be a "third state" and excluded from the customs union, May reportedly appeared surprised.

As May laid out her plans, Juncker reportedly said, "The more I hear, the more skeptical I become," and that "Brexit cannot be a success."

Berlin bureau chief for The Economist, Jeremy Cliffe, summarized the report, which he called "absolutely damning," in a series of tweets.

26) What to make of it all? Obviously this leak is a highly tactical move by Commission. But contents deeply worrying for UK nonetheless. — Jeremy Cliffe (@JeremyCliffe) April 30, 2017

Theresa May began the U.K.'s formal exit from the European Union by triggering Article 50 on May 29th, beginning a two-year countdown to Britain's departure.