"The economic situation is worsening from month to month, and unemployment has reached a level that puts democratic structures ever more in doubt," he said.
"The Germans have not yet realised that southern Europe, including France, will be forced by their current misery to fight back against German hegemony sooner or later," he said, blaming much of the crisis on Germany's wage squeeze to gain export share.
Mr Lafontaine said on the parliamentary website of Germany's Left Party that Chancellor Angela Merkel will "awake from her self-righteous slumber" once the countries in trouble unite to force a change in crisis policy at Germany's expense.
His prediction appeared confirmed as French finance minister Pierre Moscovici yesterday proclaimed the end of austerity and a triumph of French policy, risking further damage to the tattered relations between Paris and Berlin.
"Austerity is finished. This is a decisive turn in the history of the EU project since the euro," he told French TV. "We're seeing the end of austerity dogma. It's a victory of the French point of view."
Μr Moscovici's comments follow a deal with Brussels to give France and Spain two extra years to meet a deficit target of 3pc of GDP. The triumphalist tone may enrage hard-liners in Berlin and confirm fears that concessions will lead to a slippery slope towards fiscal chaos.
German Vice-Chancellor Philipp Rösler lashed out at the European Commission over the weekend, calling it "irresponsible" for undermining the belt-tightening agenda.
The Franco-German alliance that has driven EU politics for half a century is in ruins after France's Socialist Party hit out at the "selfish intransigence" of Mrs Merkel, accusing her thinking only of the "German savers, her trade balance, and her electoral future".
It is unclear whether the EU retreat from austerity goes much beyond rhetoric. Mr Moscovici conceded last week that the budget delay merely avoids extra austerity cuts to close the shortfall in tax revenues caused by the recession.
The new policy allows automatic fiscal stabilisers to kick in, but France will stay the course on the original austerity. "It is not about relaxing the effort to cut spending. There will no extra adjustment just to satisfy a number," he said.
Mr Lafontaine said he backed EMU but no longer believes it is sustainable. "Hopes that the creation of the euro would force rational economic behaviour on all sides were in vain," he said, adding that the policy of forcing Spain, Portugal, and Greece to carry out internal devaluations was a "catastrophe".
Mr Lafontaine was labelled "Europe's Most Dangerous Man" by The Sunafter he called for a "united Europe" and the "end of the nation state" in 1998. The euro was launched on January 1 1999, with bank notes following three years later. He later left the Social Democrats to found the Left Party.