David Cameron’s promise of a referendum on EU membership has been greeted with derision by many politicians in Brussels and Paris, as well as a few in Berlin. But this issue cannot be waved away quite that easily. The UK remains Europe’s most influential country. Mr Cameron’s decision will and must change Europe.

The EU provoked him into doing this by deciding to introduce the Tobin tax. Whatever you may think of this financial transaction tax — whether a foolish trifle or something of uncertain purpose or benefit — it is clearly a thorn in the UK’s flesh. It is grossly negligent to risk Britain's EU exit for the sake of it and those who pushed this tax, knowing it would provoke Britain, have endangered the European project.

The French Foreign Minister's rancorous announcement that nobody would stop Britain from leaving the EU may be understandable. But it is hard to understand why the German Foreign Minister should join in reproaching Britain - it has been one of Germany's cardinal policies to keep the UK closely tied to the European project, in part to block France's mercantilist intentions. Angela Merkel, with her offer to negotiate with Britain, showed far greater intelligence and caution. In essence Mr. Cameron is right.

There is something amiss in the EU. It regulates far too many things that fall outside its remit. The abolition of incandescent light bulbs, the rules on the curvature of cucumbers, labour market regulations and attempts to privatise water are just a few examples of nonsensical abuses of EU power. Moreover, in clear contradiction of the Maastricht treaty, the European Central Bank is being misused, printing money to finance states.

It is a mistake to strive towards political union via deeper integration of the eurozone. Measured by voting rights in the ECB Governing Council, the focus of the eurozone lies in the Mediterranean. It almost resembles an expanded Latin Currency Union, the 19th-century union that extended from France to Greece; the latter country declared bankruptcy three times back then. Germany is compelled to submit to the Mediterranean majority.

Deepening integration through the eurozone is pushing Germany out to the fringe. Germany must rethink its European policy. Europe's leaders are insisting that we step up the pace but, as Mr. Cameron points out, nobody knows where all of this is taking us.

It is better to stop, pause, reflect and then return to the last signpost and try a different route. Germany must take Mr. Cameron seriously. We need a new blueprint for a prosperous, free and united Europe.

Hans-Werner Sinn is Professor of Economics at the University of Munich