Labour have said that an account of Prime Minister Theresa May's meeting with European Council President Jean-Claude Juncker was proof that she was "leading Britain over a cliff edge".
Juncker reportedly accused May of being "deluded" on her expectations for Brexit after the pair met in Downing Street to discuss negotiations last Wednesday (26 April).
In a statement in response to the report, published by German newspaper Frankfurter Allgemeine Sonntagszeitung (FAZ), Labour's Shadow Brexit Secretary Sir Keir Starmer said: "Whatever the purpose of these leaks, this is a deeply worrying account and further evidence that Theresa May's rigid and complacent approach to Brexit negotiations risks leading Britain over a cliff edge.
"It is clearer by the day that an extreme Tory Brexit poses a severe risk to the British economy and to people's jobs and living standards.
"Theresa May talks about strengthening her hand, but in reality she has misjudged her hand at every turn, weakening Britain's position.
"By refusing to acknowledge the complexity and magnitude of the task ahead the prime minister increases the risk that there will be no deal, which is the worst of all possible outcomes."
May has not ruled out leaving the EU without a trade deal – a prospect that becomes more likely if the UK refuses to settle its €60bn (£52bn, $64bn) Brexit divorce bill for outstanding obligations.
Juncker reportedly told May that a trade deal was not going to happen unless the amount was paid.
Starmer added: "In pursuing a rigid and complacent approach, the prime minister now finds herself marginalised and isolated across the continent. Since day one, she has been driven not by the national interest, but by the interests of the Tory party.
"We urgently need a new approach. Labour will seek a new collaborative partnership with our European allies.
"We will guarantee the rights of EU nationals, immediately setting a different and more positive tone. And we will rebuild relations with the EU and make sure that jobs, the economy and rights come first."
Labour leader Jeremy Corbyn said of May: "To start negotiations by threatening to walk away with no deal and set up a low tax economy on the shores of Europe is not a very sensible way of approaching people with whom half of our trade is done at the present time."
May has reportedly dismissed the reports as "Brussels gossip".
She told Sky News: "Just look at what the European Commission themselves said immediately after the dinner took place which was the talks had been constructive.
"But it also shows these negotiations are at times going to be tough. In order to get the best deal for Britain, we've got to make sure we've got that strong and stable leadership."
Liberal Democrat leader Tim Farron also warned that May's stance on Brexit is doomed: "These reports have blown a massive hole in the Conservative Party's arguments. It's clear this government has no clue and is taking the country towards a disastrous hard Brexit.
"This election offers us a chance to change the direction of our country, keep Britain in the single market and give the people the final say over what happens next."