David Cameron and Nick Clegg have clashed over Europe as the continent struggles to deal with the eurozone crisis.
After the Prime Minister urged "fundamental reform" of EU institutions, his Liberal Democrat deputy delivered a dire warning that renegotiating treaties would cause paralysis.
Only "populists, chauvinists and demagogues" would benefit if mainstream politicians became locked into "arcane" discussions rather than focusing on economic recovery, Mr Clegg insisted.
In his annual foreign policy speech to the Lord Mayor of London's banquet on Monday night, Mr Cameron dismissed talk of "grand plans and Utopian visions" and called for a looser EU with "the flexibility of a network, not the rigidity of a bloc".
Mr Cameron - who pointedly described himself as among the "sceptics" on Europe - acknowledged that the immediate priority for the EU was restoring growth and tackling the debt crisis. But he said the current crisis also offered an opportunity to undertake fundamental reform and address long-standing problems afflicting the EU.
Mr Cameron said that while he wanted to see powers to "ebb back" to Britain, for the EU as a whole it was a chance to ask: "What kind of Europe do we actually want?" He added: "For too long, the European Union has tried to make reality fit its institutions. But you can only succeed in the long run if the institutions fit the reality."
At a press conference, Mr Clegg admitted he "thought differently" from Mr Cameron on Europe. He said: "Clearly the Conservative Party and the Liberal Democrats, and David Cameron and myself, think differently on European issues. But where we agree is... what do we do to push economic reform and push the liberalisation needed to create jobs and prosperity in the EU?"
Responding to Mr Clegg's comments, Mr Cameron's official spokesman said: "He was making the same point as the Prime Minister was making last night, which is that Europe needs to focus on the issues that matter.
"It needs to focus on reforming the economy and generating prosperity and in the immediate future it needs to focus on dealing with the European debt crisis. That means a credible plan to address that and credible fiscal plans in European countries."
The spokesman said the Government "remains concerned about the economic situation and prospects because uncertainty will act as a brake on the investment we need to support growth".