Senior figures in the EU believe that Britain will give up on Brexit if they make negotiations as tough as possible, The Daily Telegraph understands.
British officials are fighting to stop Europe adopting a no-compromise position in the hope that the UK will change its mind about leaving the bloc.
The revelation came as Jean-Claude Juncker, the European Commission president, said British politicians were to blame for Brexit because they spent 40 years spreading "lies" about the EU.
More than five prominent EU figures interviewed by The Daily Telegraph expressed doubts that Britain would go through with Brexit when confronted by the "reality of the bureaucratic nightmare" and the "insane act of economic self-harm".
One senior UK official involved in setting up forthcoming negotiations said the EU elite "seem to think the game is to make us change our minds". The stance has left representatives fighting to explain to EU leaders that their approach was "dangerous" and "unlikely" to succeed.
A second UK source added there was a risk of positions in the Brexit talks becoming "dangerously entrenched", even before Theresa May invokes Article 50 that will open formal "divorce" proceedings.
The sense that battle lines are hardening came as the 27 EU leaders prepared for a summit today (Friday) in the Slovakian capital, Bratislava, designed to show unity and a determination to forge ahead with a future without Britain.
The toughening mood was indicated by Donald Tusk, the European Council president, in a nine-point letter urging EU leaders to use the summit to restore citizens' fading faith in the Union.
In a barely disguised appeal to make sure Britain was left demonstrably worse off by Brexit, Mr Tusk insisted that the 27 should resolutely "stick to the treaty" on issues such as free movement.
"If we do so, there will be no room for doubt that it is a good thing to be a member of the Union," he wrote.
Burkhard Balz, a German MEP and influential figure on the European Parliament's economic and monetary affairs committee, said Britain must not underestimate the determination of the rest of Europe to deprive the UK of its EU financial passporting rights and euro clearing.
He also warned Europe would accept economic pain to defend its core principles and that a UK belief that the demands of German and French exporters could soften terms was overblown. "This summer I travelled all over Germany, and the main reason was to talk about Brexit. Every time, in every place, the biggest round of applause was when I said the 'the time of cherry-picking and rebates is over'. That is how the German people feel about the situation," he told The Daily Telegraph.
In the European Parliament, which must ratify any Article 50 deal agreed by the EU 27, the mood against Britain was further soured by personal attacks on Guy Verhofstadt, the former Belgian prime minister and a leading Brexit negotiator, by former Ukip leader Nigel Farage and the Brexit Secretary David Davis.
Mr Davis referred to his future interlocutor as "Satan" when addressing the foreign affairs select committee, while Mr Farage lambasted Mr Verhofstadt as a "fanatic".
"Perhaps there was a time when this could not have got nasty," said one source close to Mr Verhofstadt, "but when the Brexit minister calls the chief negotiator 'Satan', what is the response, really, that Britain expects?"
Jean Claude Juncker said it is no surprise that the country voted to leave the European Union earlier this year because the public have been told that the EU is "stupid" for decades.
Of British politicans, he said: "On Europe there are so many lies, so many half-truths that are circulated around, that one cannot be surprised."
He admitted that the union must shoulder some of the blame for the decision but claimed there is "something wrong" with the UK in comments that prompted fury among British MPs.
In a YouTube question and answer session Mr Juncker said: "Of course Brexit means that something is wrong in Europe. But Brexit means also that something was wrong in Britain.
"If, over 40 years, you are explaining to your general public that the EU is stupid... you can't be surprised that the day you ask people 'do you want to stay or do you want to leave?' that a too high number of British expressed the view that it is better to leave."
"On Europe there are so many lies, so many half-truths that are circulated around, that one cannot be surprised."
Douglas Carswell, the Ukip MP, called Mr Juncker "arrogant" following his remarks.