David Cameron has given his strongest warning yet that the euro is doomed to fail as fears grow that Greece is close to crashing out of the single currency.

The Prime Minister dismissed new French president Francois Hollande's claim that Britain was 'indifferent' to the fate of the eurozone, insisting it was essential for our economy that the Continent recovers.

'We want the euro area to succeed,' Mr Cameron said in an interview with the Daily Mail. 'It's 40 per cent of our exports. It's vitally important these economies get back to growth.

'The difficulty for us is we take a different view about the euro. We didn't join. We think that single currencies really require single governments if they are going to work properly.

'We have to recognise that the euro is a project in enormous transition. It could go in any number of different ways.

Making sense of the euro for me would mean that those eurozone countries would have to have much more co-ordinated economic policy, much more co-ordinated debt policy.

'There's nowhere in the world that has a single currency without having more of a single government.'

Markets slumped yesterday as doubts grew about Franco-German relations following the victory of socialist President Hollande over Nicolas Sarkozy.

EU leaders will gather later this month for an emergency summit to discuss the new French leader's proposal to tear up an EU 'fiscal pact' to allow for a greater focus on growth, rather than austerity.

Athens, meanwhile, was gripped by political chaos. The far-Left Syriza group was seeking to form a new government after Greece's two main parties saw support crash in Sunday's elections.