David Cameron issued a stark warning to European counterparts that Brussels is "too big, too bossy, too interfering" as he made clear his opposition to the front runner in line to take the union's top job.
The Prime Minister warned fellow leaders they cannot " shrug off" the dire results of the euro elections and over dinner will demand they are more ruthless about the European Union's priorities.
Discussions will focus on setting out the process for finding a replacement for European Commission president Jose Manuel Barroso when his term ends in October, but Mr Cameron signalled he is deeply opposed to current front runner Jean-Claude Juncker, an EU veteran with federalist ambitions.
I n a thinly-veiled swipe, the premier stressed the importance of securing a candidate focused on openness and flexibility instead of being bound up in the union's past.
Although Mr Cameron cannot formally veto Mr Juncker, who h as been nominated as the candidate of the European People's Party grouping - the block the PM previously pulled the Tories out of over its federalist sympathies - it is unlikely that the European Council, made up of the EU's 28 national heads of government, would force through a new president without unanimous backing.
Arriving for the talks, the Prime Minister told reporters: "Europe cannot shrug off theses results. We need an approach that recognises that Europe should concentrate on what matters, on growth and jobs and not try and do so much.
"We need an approach that recognises that Brussels has got too big, too bossy, too interfering. We need more for nation states. It should be nation states wherever possible and Europe only where necessary.
"Of course we need people running these organisations that really understand that and can build a Europe that is about openness, competitiveness and flexibility, not about the past."
Ukip leader Nigel Farage earlier claimed there was " nobody more fanatical about building the United States of Europe" than Mr Juncker and insisted his candidacy has come "just at the moment that the European electors have made it clear they are going in the wrong direction".
Tonight's gathering of 28 leaders will also focus on the political earthquake which saw Ukip top the polls in Britain, the far-right Front National come first in France and the extreme-left Syriza movement take top spot in Greece.
The Eurosceptic Five Star movement came second in Italy and the anti-euro Alternatives won seven seats in Germany - although broadly pro-European parties still dominate the parliament.
Before travelling to the meeting Mr Cameron made a series of phone calls to counterparts across the union, including German chancellor Angela Merkel, French president Francois Hollande, Polish PM Donald Tusk, Lithuanian president Dalia Grybauskaite, Hungarian PM Viktor Orban, Swedish PM Fredrik Reinfeldt, Slovenian PM Alenka Bratusek and Irish Taoiseach Enda Kenny, as he attempted to rally support for reform.
The PM has promised to renegotiate Britain's relationship with Europe then give voters an in/out referendum on membership in 2017.
Shadow foreign secretary Douglas Alexander said: " As European leaders meet in Brussels, there is no doubt that Europe now faces a significant reform moment that must be seized.
"But going into this vitally important EU meeting, David Cameron seems either unwilling or unable to set out what changes he wants to see at an EU level.
"Only days after the European elections, it is clear that Europe has to work better for Britain, but instead of building alliances with our European partners for reform, his party is proposing pacts with Ukip candidates and deals with fringe political parties in the European Parliament.
"It is not too late for David Cameron to change course and use this week's EU meeting to set out a clear agenda for reform and build the necessary alliances to deliver it."