One of Germany's most influential political thinkers has delivered a stark warning that its post-second world war liberal democracy cannot be taken for granted and its dominant role in managing Europe's debt crisis could lead to disaster.

Jürgen Habermas, the Frankfurt professor whose political thinking has helped shape Germany over the past 50 years, called for the EU to be turned into a supranational democracy and the eurozone to become a fully fledged political union, while lambasting the "technocratic" handling of the crisis by Brussels and European leaders.

In his first big speech on the euro crisis, delivered at Leuven University, east of Brussels, Habermas called for a revival of Europe's doomed constitutional ambitions, arguing that the disconnect between what needed to be done in economic policy and what was deemed to be politically feasible for voters was one of the biggest perils facing the continent. "Postponing democracy is rather a dangerous move," he said.

At 83, Habermas has long been revered as a guru and mentor to the post-1968 generation of centre-left German politicians. He is a champion of a democratically underpinned European federation, and has reserved some of his most trenchant criticism for Berlin's role in the three-year crisis.

"The German government holds the key to the fate of the European Union in its hands. The main question is whether Germany is not only in a position to take the initiative, but also whether it could have an interest in doing so," he said.

"The leadership role that falls to Germany today is not only awakening historical ghosts all around us, but also tempts us to choose a unilateral national course or even to succumb to power fantasies of a 'German Europe'.

Habermas says the EU elite’s response to the currency crisis has been to construct a technocracy without democratic roots. Photograph: Reuters

"We Germans should have learned from the catastrophes of the first half of the 20th century that it is in our national interest to avoid permanently the dilemma of a semi-hegemonic status that can hardly hold up without sliding into conflicts."

Habermas's wakeup call came at the end of a week of similar alarms being sounded on both sides of the country's borders. The Polish prime minister, Donald Tusk, in the presence of the German chancellor, Angela Merkel, in Berlin last week, said there were worries about German domination of the EU "everywhere, without exception".

A leaked draft policy paper from France's governing socialist party on Friday was redolent with fear of and hostility to Merkel and her policy prescriptions in the euro crisis.

Habermas demanded a sea change in German policy, away from insisting on "stabilising" the budgets of vulnerable eurozone countries by slashing social security systems and public services, to a policy of "solidarity" entailing common eurozone liability, mutualised debt, and euro bonds.

He located Germany's traditional EU enthusiasm in the post-Nazi quest for international rehabilitation through reconciliation with France and driving European unification processes, all occurring under the protection and promotion of the US in cold-war western Europe until the Soviet collapse in 1989.

Habermas said: "The German population at large could develop a liberal self-understanding for the first time. This arduous transformation of a political mentality cannot be taken for granted … Germany not only has an interest in a policy of solidarity, it has even a corresponding normative obligation … What is required is a co-operative effort from a shared political perspective to promote growth and competitiveness in the eurozone as a whole."

Such an effort would require Germany and several other countries to accept short- and medium-term redistribution in its long-term interest, he added, "a classic example of solidarity".

The structural imbalances between the economies of greatly divergent eurozone countries at the root of the crisis were certain to worsen under the policies being pursued, Habermas argued, because governments were making decisions "exclusively from [their] own national perspective. Until now, the German government has clung steadfastly to this dogma".

He said the EU elite's response to the crisis had been to construct a "technocracy without democratic roots", trapping Europe in a dilemma of legitimacy and accountability, between "the economic policies required to preserve the euro and, on the other, the political steps to closer integration. The steps that are necessary are unpopular and meet with spontaneous popular resistance".