Theresa May has accused European politicians and officials of making deliberate "threats" against the UK in order to influence the result of the general election.
The prime minister made the comments outside 10 Downing Street after visiting the Queen at Buckingham Palace to mark the dissolution of the 2015 parliament.
She said the central issue of the 8 June election would be the looming Brexit negotiations, and that "in the last few days we have seen just how tough these talks are likely to be".
"Britain's negotiating position has been misrepresented in the continental press," May continued. "The European Commission's negotiating stance has hardened.
"Threats against Britain have been issued by European politicians, and officials. All of these acts have been deliberately timed to affect the result of the general election that will take place on 8 June."
One EU leader told BuzzFeed News that her remarks were: "quite amazing", adding they thought it was a reaction to leaked reports of an awkward-sounding dinner meeting between May and European Commission president Jean-Claude Juncker at the end of April.
A European government official described the speech as "very odd, and quite worrying, frankly."
The official went on: “I think there is some misunderstanding regarding the EU’s stance so far: No one has made any threats, on the contrary, there is a feeling of genuine and friendly concern as to the negotiating strategy on the UK side."
They said the EU was just continuing to prepare for the negotiations, adding: "So logically the EU’s negotiating stance comes out in the public in more details now, because it is time for the 27 to agree on it."
They added that the general election was "a purely internal question for the UK citizens to decide."
Labour leader Jeremy Corbyn accused May of "playing party games with Brexit".
Earlier this week, the German newspaper Frankfurter Allgemeine reported on a dinner meeting between May and European Commission president Jean-Claude Juncker that took place last month, after which he reportedly told the prime minister he left "ten times more sceptical than I was before".
May told reporters on the campaign trail yesterday that the account was "Brussels gossip".
Earlier on Wednesday the gulf between the UK and Brussels was exposed as Brexit secretary David Davis and the EU's chief negotiator Michel Barnier held separate events outlining their positions on upcoming talks.
Speaking outside Downing Street, May said she had made it "clear" to European Council president Donald Tusk when Article 50 was triggered that Britain wants "a deep and special partnership with the European Union, and we want the EU to succeed".
"But the events of the last few days have shown that whatever our wishes, and however reasonable the positions of Europe's other leaders, there are some in Brussels who do not want these talks to succeed, who do not want Britain to prosper," the PM said. "Now more than ever we need to be led by a prime minister and a government that is strong and stable."
She added: "While there is enormous opportunity for Britain as we leave the EU, if we do not get this right the consequences will be serious, and they will be felt by ordinary working people across the country."
Labour leader Corbyn said May was deliberately "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," he said in a statement.
“But Brexit is too important to be used as a political game in this election.
“These are vital negotiations for every person in Britain and for the future of our country. But Theresa May is putting party interest ahead of the national interest."
Scottish first minister Nicola Sturgeon said May was trying to make the EU into "a bogeyman" to distract voters from other issues.
1/4 UK needs best possible Brexit deal and has limited leverage, so for PM to poison atmosphere for partisan reasons is deeply irresponsible
2/4 Having called election for reasons of party not national interest, PM now seems intent on fighting campaign in same way
3/4 Making a bogeyman of EU is all about distracting attention from Tories' wider record - while PM continues to hide from voters.
4/4 A Tory gov without strong opposition is against interests of all parts of UK. In Scotland, strong opposition will only come from @theSNP