Prime minister attacks the frontrunner for the leadership, who he says has been dedicated to increasing the power of Brussels

David Cameron has launched a strong personal attack on Jean-Claude Juncker, declaring that the former prime minister of Luxembourg is the wrong person to lead the European commission.

As he arrived at the EU summit in Brussels, the prime minister acknowledged that the odds were "heavily stacked against" Britain but he said he was determined to stand against Juncker on the grounds that the frontrunner for the commission job has spent his life seeking to increase the powers of the EU.

The prime minister made clear that he would force a vote at the European council on Friday afternoon as even his allies said that they would now be supporting Juncker. Fredrik Reinfeldt, the Swedish prime minister who had voiced concerns about Juncker, indicated he would support him on the grounds that his candidacy would be approved by EU leaders and the European parliament.

But Cameron insisted he would continue to oppose Juncker on the grounds that he would not be able to lead EU reform and that the spitzenkandidaten system is on the verge of delivering the European commission presidency to the EU veteran. The system was devised by European parliament leaders who are using the powers in the Lisbon treaty that says that EU leaders need to take account of last month's European parliamentary elections in nominating a candidate. Juncker is the candidate of the centre right European People's party, the largest group in the parliament.

The prime minister outlined his objections to Juncker when he said: "You stick to your convictions even if the odds are heavily stacked against you rather than go along with something that you believe is profoundly wrong. Today is one of those days.

"I will tell you why it is so important. The European elections showed that there is huge disquiet about the way the EU works and yet the response, I believe, is going to be wrong on two grounds. Wrong on the grounds of principle: it is not right for the elected heads of government of the European countries to give up their right to nominate the head of the European commission – the most important role in Europe. That is a bad principle.

"And it is the wrong person. Jean-Claude Juncker has been at the heart of the project to increase the power of Brussels and reduce the power of nation states for his entire working life. He is not the right person to take this organisation forward. So, I am very clear about the right thing to do."

The prime minister's personal attack marks an escalation of Britain's opposition to Juncker. Cameron has concentrated in recent weeks on highlighting his concerns about the spitzenkandidaten system.

In a sign of how highly charged the atmosphere is expected to be at Friday's lunch, it was confirmed on Thursday night that EU leaders have voiced concerns over Juncker's drinking habits in the last month. He was famous for ensuring a ready supply of wine during his eight-year presidency of the Eurogroup of eurozone finance ministers until last year.

"His alcohol consumption has been raised by a number of leaders since the parliamentary elections [last month]," said an EU diplomat.

There were also reports that Juncker chain-smoked through a meeting of EPP leaders in the Flanders town of Kortrijk on Thursday before the Ypres summit dedicated to marking the centenary of the start of the first world war.

EU diplomats suggested his campaign team has been examining changing the rules of the commission's Berlaymont headquarters to allow Juncker to smoke in the president's suite of offices.

Cameron signalled on Thursday that he would warn EU leaders at their summit in Brussels that the appointment of Juncker as next head of the EU executive would increase support for a British withdrawal from the EU.

As Germany and France brushed aside British threats to call a vote on the Juncker nomination at a Brussels lunch on Friday and amid signs that EU leaders will offer overwhelming support for the former Luxembourg prime minister, Cameron warned of "consequences" if Juncker is endorsed.

He prepared the ground for a strong warning at the end of the summit on Friday afternoon about the consequences of his appointment, telling the BBC: "Everything has consequences in life. And obviously, I think proceeding in the way that countries are planning to proceed in choosing this individual is the wrong approach. I think that would be bad for not just [Britain], but all of Europe."

But the leaders of Germany and France made it plain that they were prepared to win a vote if Cameron insisted. While emphasising that the decision on Juncker would be made on Friday, Angela Merkel offered Cameron a consolation prize, stressing she wanted to reach compromises on his reform agenda for the next five years.

"If we have clarity on the necessary content for the next five years, we will take the decision on the next European commission president," the German chancellor said. "We can find good compromises with Great Britain and move a bit towards Great Britain."

François Hollande, the French president, said: "If there is a British request on this topic, I am for a vote. There are times when Europe has to say what it wants."

He dismissed speculation about the UK invoking an obscure mechanism from the 1960s enabling a member state to cite vital national interests to stall a summit decision. "It's not a defining choice for the future of a country meriting a veto," Hollande said.

Martin Schulz, the German social democrat and speaker of the European parliament who has played a central role in pushing Juncker to be the next president of the commission, said: "Let's be honest, [Cameron's] is not a normal political attitude. It's up to him whether he wants to marginalise himself."

The concerns about Juncker come as little surprise to EU veterans. One source told the Guardian: "Juncker was a perfectly good chairman of the Eurogroup during the crisis. He is not a visionary but Luxembourg doesn't do visionaries. Anyway, Britain says it doesn't want any visionaries."