London - Britain could be "isolated and marginalised" by the European Union after vetoing treaty change aimed at ending the euro debt crisis, Deputy Prime Minister Nick Clegg said on Sunday.
The Liberal Democrat party leader's comments saw him officially breaking ranks with Conservative Prime Minister David Cameron, who was responsible for the veto at a summit in Brussels on Friday.
"I am bitterly disappointed by the outcome of last week's summit, precisely because I think there is now a real danger that over time the United Kingdom will be isolated and marginalised within the European Union," Clegg told the BBC.
Clegg - who had until now limited himself to expressing "regret" over the veto - rejected Cameron's arguments that it was necessary to protect Britain's vital City of London financial services hub.
"I don't think that's good for jobs in the City or elsewhere. I don't think it's good for growth. I don't think it's good for families up and down the country," he said.
Clegg said he had told Cameron by telephone after he was informed of the veto in the early hours of Friday that it was "bad for Britain".
But he said Cameron's hand was forced by the "intransigence" of France and Germany - which both pushed for the deal to bring in strict fiscal discipline for the eurozone - and also by eurosceptic Conservative lawmakers.
"I think the prime minister was in a difficult position because he faced intransigence from France and Germany," Clegg said. It was "clear that the French government, for instance, would not shed a tear if Britain was pushed".
Clegg said the centrist, pro-Europe Liberal Democrats would remain in the coalition that was formed in May 2010, saying it would be "even more damaging for us as a country if the coalition government were now to fall apart".
But he urged Cameron to re-engage with Europe.
"Far from retreating further to the margin, which is what some eurosceptics want and are calling for, we should be re-engaging more fully, and we're going to have to redouble our efforts in doing so," Clegg said.
The deputy premier also warned against anti-EU elements in the centre-right Conservatives pushing for Britain to leave the bloc altogether, saying it would leave Britain as a global "pygmy".
"I think a Britain which leaves the EU will be considered to be irrelevant by Washington and will be considered a pygmy in the world, when I want us to stand tall and lead in the world," he said.