British Prime Minister David Cameron promised on Wednesday (25 June) to oppose Jean-Claude Juncker becoming the next president of the European Commission "to the end" after a minister in his own coalition government queried the way he handled Europe policy.

Addressing parliament on the eve of a summit of EU leaders in Belgium on Thursday and Friday at which Juncker is expected to be appointed to the top EU job, Cameron signalled again he would not back down, even though his attempts to rally support against Juncker have fallen flat.

"I think it's important on this issue to stand up and speak for what you believe in," Cameron said, calling the European Parliament-inspired move to give Juncker the senior role "a power grab" at the expense of elected EU leaders.

"I also think it's important that the people involved understand that we need reform in Europe and it doesn't matter how hard I have to push this case. I will take it all the way to the end," he said.

The Conservative leader has demanded that European leaders vote on whether Juncker should become the next president of the EU executive, arguing he is too integrationist and reform-resistant. That has Cameron isolated and frustrated in Brussels.

Cameron, who has promised to try to recast Britain's EU ties and offer Britons an in/out EU membership referendum, made his latest defiant promise to oppose Juncker after Business Secretary Vince Cable, a member of the Liberal Democrat party, Cameron's junior coalition partner, criticised him.

"I think he [Cameron] was right to take the position he did. But the way it's been done unfortunately has not helped Britain punch its weight in Europe," Cable told BBC radio.

When asked whether he accepted Cable's analysis, Cameron's official spokesman made it clear the prime minister was irritated by the intervention from a coalition minister and thought his own approach on Europe correct.

Nigel Farage, the leader of the UK Independence Party (UKIP), which won last month's European elections in Britain, said Cameron was riding for a fall.

"Cameron has completely misjudged this. He looks absolutely ludicrous, he has said he will fight this to the bitter end and he is going to lose," Farage told an audience of investors at an financial conference in London.

Coalition tensions

Two of Cameron's ministers spoke out on Europe, too.

Nicky Morgan, the newly-appointed minister in charge of financial services, said she would push the EU to improve the way it set financial rules, promising to protect London's role as a global financial sector, and demanding better assessments of the impact of new regulations.

David Lidington, Britain's minister for Europe, told an audience in Berlin that choosing Juncker for the Commission job risked turning the EU executive into "a creature" of the European Parliament.

Cable's intervention reflected tensions inside the coalition ahead of next year's national election.

The Liberal Democrats have cast themselves as Britain's most pro-European political party in contrast to Cameron's Conservatives, who have tried to strike a more Eurosceptic tone to respond to the rise of UKIP.

Those tensions were expected to surface again later on Wednesday when Danny Alexander, a senior Liberal Democrat minister at the finance ministry, gives a speech in which he will say officials have calculated that 3.3 million British jobs depend on the country's membership of the 28-nation bloc.

Some EU insiders think Cameron's handling of the Juncker appointment has embarrassed allies and emboldened adversaries, while weakening his credibility on Europe at home and abroad.

An opinion poll published in Wednesday's Financial Times newspaper suggested, however, that some British voters think he has played it well.

The Populus/FT survey found that 49% thought he was "strong" by taking a stand, while only 22% thought he would be perceived as weak if, as expected, he failed to win the vote, a finding his political opponents will find uncomfortable.