May hosted European Commission chief Jean-Claude Juncker at Downing Street on Wednesday to discuss the forthcoming negotiations on Britain's withdrawal from the European Union.
At the time, her aides described the meeting as "constructive" -- but a report in Germany's Frankfurter Allgemeine Zeitung painted a much more negative picture.
It said Juncker was left deeply pessimistic about the prospects of a Brexit deal, after May refused to offer any compromise on Britain's exit bill and the timing of trade talks.
"I have to say that from what I've seen of this account, I think it's Brussels gossip," May said when asked if the report was true.
"And just look at what the European Commission themselves said immediately after the dinner took place, which was that the talks had been constructive.
"But it also shows that these negotiations are at times going to be tough."
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Juncker reportedly relayed his thoughts to German Chancellor Angela Merkel -- who the next day warned Britain publicly that it should have no "illusions" of what Brexit would involve.
May was speaking in Lancashire, north-west England, while campaigning for the general election in June, which she is hoping will give her a new mandate for the Brexit talks.
British opposition politicians seized on the German report to condemn May's approach, which involves pulling Britain out of Europe's single market to try and control migration.
Senior Labour lawmaker John McDonnell said the account was "deeply worrying" and showed May's "reckless handling of the EU negotiations".
Tim Farron, leader of the smaller, pro-European Liberal Democrats, added: "It's clear this government has no clue and is taking the country towards a disastrous hard Brexit."
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