Yesterday's European vote was not an election, it was a referendum. Britain's Ukip will in time slide from the stage, as will France's National Front. The vote does not upheave party politics: it was the emphatic assertion of Euro-scepticism, the moment when a critical mass of Europe's voters withdrew their consent from ever greater union.

Voters long accustomed to trust their ruling elites on Europe do so no longer. So-called mainstream parties may still dominate the EU parliament, but the writing is on the wall. The various referendums (and opinion polls) that initially rejected the Lisbon treaty were not flashes in the pan. Unless Europe's leaders mean further to enrage rightwing – and leftwing – nationalism, they must somehow reverse the ratchet of EU harmonisation and return power to nation states.

The EU's own Eurobarometer poll shows barely half the continent now in favour of union, with big majorities distrusting the parliament and opposing open borders. Over the last decade the presidency and ministerial council have taken not the slightest notice – the juggernaut has thundered on. Shedloads of regulations continue to flow from Brussels. The union has expanded eastwards, flooding west Europe's stressed labour markets. Anyone who objected was dismissed as racist. It was a gift to the right wing.

Europe is not culturally homogeneous and federalist, like America. Its peoples are pluralist. Throughout history they have revolted against attempts to weld them into one – from Romans and Bourbons to Napoleon, Hitler and Stalin. If forced into a supranational straitjacket they rebel. The EU can at least draw comfort from last night's rebellion being peaceful, one of ballot not bullet.

For European economic cooperation to break down would be a tragedy, but it would be laid squarely at the door of leaders who allowed their ambitions to diverge from the opinions of their peoples. Reformers must urgently ease the pressure of labour migration and the weight of Euro-regulation. If they do not, they will unleash forces not seen on such a scale in Europe since the 1930s.

These votes cannot be brushed aside as a protest blip. Europe is a democracy. That is the most encouraging message of last night.