Health Secretary Jeremy Hunt has labelled Europe's leaders "cowards" for electing arch-federalist Jean-Claude Juncker as president of the European Commission.
Prime Minister David Cameron's only ally was Hungary as he attempted to block Mr Juncker, who he claims is not the right man to force through EU reform.
The Tories have promised a referendum on EU membership should they win the next election - and Mr Hunt believes "cowardice" from Europe's leaders can only make a vote to quit more likely.
"As a result of cowardice yesterday from other European leaders who weren't prepared to say in public what they said in private, they're going to have to work a lot harder to persuade the British people that Europe has a reform agenda," he said.
Mr Hunt claimed the British people would be "proud" of the Prime Minister - and that his position would ultimately help the UK renegotiate its relationship with Europe.
Former Luxembourg premier Mr Juncker was backed by Germany's Angela Merkel "You're getting European leaders queuing up to say how much they want Britain to stay in the EU, how they'll make compromises," he said.
"We want to be a country in control of our own destiny, we want to stop abuses of the welfare system and NHS.
"We're not going to take part in some grubby face-saving deal where we pretend we've got a deal - a feature of the last government. We want substantive reform in Europe."
Sky's Senior Political Correspondent Jason Farrell said Mr Hunt was not alone with his contentions.
"It might not seem like the most diplomatic language but he's not the only one saying it," he said. "Der Spiegel magazine in Germany has said Angela Merkel voted for a Commission president she didn't want - others have said European leaders have gone for the compromise."
The Prime Minister said his fellow EU leaders had made a "serious mistake" but vowed to keep fighting for reform in Europe.
The PM argued Mr Juncker was not the "right person" for the post "This is going to be a long, tough fight and frankly sometimes you have to be prepared to lose a battle in order to win a war," he added. "It has only stiffened my resolve to fight for reform in the EU, because it is crying out for it."
German Chancellor Angela Merkel was an advocate of Mr Juncker, but amid the vote she urged EU colleagues to "compromise" with Britain.
"I think we can find compromises here and make a step towards Great Britain," she said.
Labour leader Ed Miliband said: "The last 48 hours doesn't show Europe is unreformable, it shows David Cameron is not the man to reform it because he has become toxic.
"Because people doubt his motivations, because people doubt the way he operates, it's made people say 'We're not going to ally with Britain'."
UKIP leader Nigel Farage said: "I think what's clear is that any cards that Mr Cameron may have had to play have been spent, and have been lost over a futile battle that he was bound to lose from the beginning.
"(Any) renegotiation now doesn't look very likely. He has been humiliated today but worse than that, he actually looks very isolated."
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