The Prime Minister said the UK’s position had been misrepresented and the European Commission’s position had hardened.
Theresa May put the Brexit battle at the heart of the election campaign with an explosive claim that European politicians and officials were seeking to meddle in the outcome of the June 8 contest.
The Prime Minister used a Downing Street statement to claim that “threats” had been issued against the UK and Brussels’ position had hardened in acts “deliberately timed” to influence the General Election.
Mrs May said recent events showed why she should be returned to Number 10 in order to lead the crucial Brexit negotiations.
“Making Brexit a success is central to our national interest and central to your own security and prosperity,” she told voters.
“If we do not get this right, the consequences will be serious.”
The comments drew a furious response from political rivals.
Labour leader Jeremy Corbyn said Mrs May was “playing party games with Brexit” and “winding up the public confrontation with Brussels” in an attempt to distract from Tory economic failures.
SNP leader and Scottish First Minister Nicola Sturgeon accused the PM of trying to “poison the atmosphere for partisan reasons” in a “deeply irresponsible” move.
Mrs May’s speech came after she returned from an audience with the Queen at Buckingham Palace to mark the dissolution of Parliament.
It follows leaks from a Downing Street dinner last week attended by European Commission president Jean-Claude Juncker and Brexit negotiator Michel Barnier which revealed the tensions between the two sides.
She said the events had shown that “there are some in Brussels who do not want these talks to succeed” so “now more than ever we need to be led by a prime minister and a government that is strong and stable”.
Setting out the choice between her and Jeremy Corbyn, Mrs May said: “If we don’t get the negotiation right, your economic security and prosperity will be put at risk and the opportunities you seek for your families will simply not happen.”
With Mr Corbyn representing the UK at Brussels, “we will all pay a high price”, she warned.
There was no immediate response from the European Commission to Mrs May’s outspoken attack on Brussels’ officials.
Her Brexit assault followed reports that the commission could hand Mrs May a bill of up to 100 billion euro (£84.5 billion) as the fee for leaving the EU.
Mr Corbyn said: “Theresa May is playing party games with Brexit in the hope of winning advantage for the Tories in the General Election.
“By winding up the public confrontation with Brussels, the Prime Minister wants to wrap the Conservative party in the Union Jack and distract attention from her government’s economic failure and rundown of our public services.
“But Brexit is too important to be used as a political game in this election.”
Lib Dem leader Tim Farron told BBC Radio 4’s PM: “This is deeply disturbing, it’s not worthy of the office of Prime Minister and I don’t think too many people will take it terribly seriously.”