The bitter stand-off over Greece has given new energy to radical political groups on the left and right, creating a pre-revolutionary atmosphere that Europe has not seen since 1968, the EU leader who brokered Monday's bailout deal has warned.
Donald Tusk, the former Polish prime minister who now heads the European Council, said he feared "political contagion" from the Greek crisis far more than its financial fallout, arguing that common cause between far-right and far-left groups has been a precursor to some of Europe's darkest moments of the last century.
"I am really afraid of this ideological or political contagion, not financial contagion, of this Greek crisis," said Mr Tusk.
"It was always the same game before the biggest tragedies in our European history, this tactical alliance between radicals from all sides. Today, for sure, we can observe the same political phenomenon."
Mr Tusk, who chairs all EU summits, played a central role in forcing Alexis Tsipras, the Greek prime minister, and Angela Merkel, his German counterpart, to agree terms on Monday that will allow talks to restart on a new €86bn bailout as soon as this weekend.
The new bailout deal, which involves sweeping austerity measures including a requirement to put an estimated €50bn of Greek public assets into a privatisation fund supervised by EU authorities, has led to accusations in Athens that Ms Merkel forced on Greece the kind of punitive conditions Germany was saddled with at the end of the first world war.
Mr Tusk disputed such criticisms, saying he was "100 per cent sure that Germany is not the winner in the context of political power", particularly since "Germany has to sacrifice much more than other countries" in terms of financial aid it will soon have to send to Athens.
"I can't accept this argument, that someone was punished, especially Tsipras or Greece. The whole process was about assistance to Greece," Mr Tusk said.
"When we discuss facts, deeds and numbers, this is the only number on the table: €80bn for Greek assistance, and quite soft conditions. Not only [soft] financial conditions, but political conditions - in fact, without collateral. Come on: what is the reason to claim it's something humiliating for Greece, or this is punishment for Tsipras?"
Mr Tusk said he had been unsettled by the bitter recriminations that have characterised the contentious six-month Greek negotiations, particularly the anti-EU and anti-German sentiment that he believes has become part of mainstream political discourse.
He said he was taken aback by a speech Mr Tsipras gave to the European Parliament last week where his criticism of Germany - including an argument that whereas Germany was provided "solidarity" and debt relief after the second world war, Greece had been denied similar treatment - was loudly cheered by a large number of MEPs.