BRUSSELS has told Theresa May to calm down and not let “emotions get out of hand,” warning that if arguments broke out before the Brexit talks began, it would make the process impossible.

After the Prime Minister hit out at what she claimed were threats from Eurocrats designed to interfere in the UK General Election, Donald Tusk responded by calling for discretion, moderation and goodwill to help ease tensions ahead of Britain's exit.

"These negotiations are difficult enough as they are. If we start arguing before they even begin they will become impossible,” declared Mr Tusk.

"The stakes are too high to let our emotions get out of hand because at stake are the daily lives and interests of millions of people on both sides of the Channel.

"We must keep in mind that in order to succeed; we need today discretion, moderation, mutual respect and a maximum of goodwill."

His remarks followed an intervention by Antonio Tajani, President of the European Parliament, who insisted Brussels was “not seeking to influence the result in the UK".

He told a news conference in the Belgian capital that the EU actually saw Britain's snap election as "a positive development for them and for us, because this will mean there is stability in the UK".

Mr Tajani, who visited Mrs May in Number 10 last month, told reporters: “It is better to have an interlocutor, who is not constantly looking for votes because they have had the election, in order to work towards a good solution...

“If you have an election campaign, the rhetoric gets sharper and more robust. I don't think there is any question of influencing the campaign.”

Earlier, Margaritis Schinas, Mr Juncker's spokesman, also brushed aside Mrs May's controversial comments, telling reporters: "We are not naïve; we know that there is an election taking place in the United Kingdom. People get excited whenever we have elections.”

He explained that Brussels bureaucrats were “very busy…with our policy work” to try to interfere in the British election.

"We have too much to do on our plate. So, in a nutshell, we are very busy. And we will not Brexitise our work,” he declared, noting: "To put it in the words of an EU diplomat: the 30-minute slot that we are going to devote to Brexit per week, for this week it's up."

Pressed on whether Mrs May was right to claim that EU figures were using "threats" to influence the election, Mr Schinas replied: "I said that we are not naive and we know that it is time that elections happen. People get excited over elections; it's normal, so things are said.

"We don't Brexitise our very important policy work. We are too busy now to engage in these comments on who said this or that," he added.

The row over alleged Brussels interference in the election blew up after a German newspaper published an apparently well-briefed account of Mrs May's meeting over dinner with Mr Juncker and Brexit negotiator Michel Barnier in Downing Street last week, which reportedly ended with the Commission President saying he was "10 times more sceptical" of the likelihood of a successful Brexit.

On Wednesday, speaking outside Number 10, the PM retaliated and said: "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.”

She claimed that Britain's negotiating position in Europe had been misrepresented in the continental press and that it was clear the Commission's negotiating stance was hardening.

"Threats against Britain have been issued by European politicians and officials,” she declared. "All of these acts have been deliberately timed to affect the result of the General Election that will take place on June 8."

Mrs May insisted she would not let Brussels "run over" the UK in Brexit talks. "If we don't get the negotiation right, if we let the bureaucrats of Brussels run over us, we will lose the chance to build a fairer society with real opportunity for all."

The rhetoric was seen by Westminster-watchers as an attempt by the PM to win over Ukip and Labour leave voters on the eve of the local elections in Scotland, England and Wales and in the run-in to the General Election vote.

Elsewhere, Radek Sikorski, the former Polish Foreign Minister, acknowledged the leaking of the details of the No 10 dinner was “unhelpful” but argued that it should not be allowed to “highten emotions” as this in the long run would be counterproductive.

“There needs to be a little bit of trust and goodwill on both sides because, otherwise, we will have a really mean trainwreck.”

Erna Solberg, Norway’s Prime Minister, said Brexit was "challenging" not only for the UK and EU but also for her country, whose biggest trading partner was Britain.

"Norway, as a member of the internal market through the EEA[European Economic Area], will be directly affected by the UK's departure from the Union.

"We are, of course, very concerned about how the arrangements will be in the future between the EU and the UK...We believe it is possible to find good arrangements in the future," she explained.

Ms Solberg said she was happy to have received assurances from Mr Tusk and Mr Juncker that the EU would offer an "open door" for Norway - as well as fellow EEA members Iceland and Liechtenstein - to contribute its voice to the Brexit process.