Never mind the devastation that a break-up of the eurozone would wreak; never mind the unimaginable economic, social and political consequences if the vision of a united Europe were lost to the design faults of the single currency; and never mind the knife-edge upon which the euro is now so finely balanced. Regardless of the risks, Eurosceptics both inside and outside Government are trying to use the crisis to prise Britain out of Europe altogether. The shameless opportunism of such agitation is bad enough. More unforgivable still, it makes the task of solving Europe's problems more difficult than ever.

Senior Conservative members of the Coalition are as egregious offenders as any. George Osborne has already weighed in once, with his oft-quoted identification of the "remorseless logic" of closer European integration (providing that does not include us). Now the Chancellor has gone a step further, explicitly raising the possibility of an in/out referendum on Britain's membership of the EU. His aides claimed the comments were hypothetical only. But no amount of post hoc justification can scrub away the taint of politics. Such game-playing may be acceptable in opposition; it is not worthy of a Chancellor. Nick Clegg may struggle for authority in government, but he should still be shouting louder about Britain's place in Europe.

In fact, the Government's position – as articulated by the Prime Minister and Chancellor, at least – is a confusing one. With the black hole in Spain's banks threatening to pitch the eurozone into a sovereign funding crisis it will struggle to contain, both David Cameron and Mr Osborne have lent whole-hearted support to plans for a euro-wide banking union. They are also four-square behind more general efforts to deepen and extend the common market. When it comes to Britain's financial services, however, all bets are off.

David Cameron has already vetoed the European fiscal pact, after his six conditions designed to protect the City (described by one British MEP as a "rat sandwich") were comprehensively rejected. For all the raucous plaudits, from Eurosceptic backbenchers and newspapers alike, Mr Cameron's "standing up for Britain" only forwent our voice in negotiations, to some chagrin in the City. Efforts to ensure Britain is not touched by a banking union look alarmingly like more of the same.

The Government is not wrong to fight for our financial services sector. For all the justifiable ire now directed against banks and bankers, the City remains the engine of the British economy. Resurgent manufacturing industries are much to be desired, but such a shift is neither quick enough, nor sure enough, to be relied upon. Meanwhile, banks account for 10 per cent of GDP, employ up to a million people and produce an annual surplus of £40bn. Such numbers are not to be treated lightly.

But David Cameron et al are turning what should be the starting point of negotiations into an ideological crusade that has less to do with finding a solution than with capitalising on the perceived weakness of the others at the table. Between compromise and careful design, there may be integration and regulation that work for all. Rabble-rousing at home is no way to achieve it.

More importantly, it is not only our financial services at stake. What should be a nuanced discussion about banking regulation is becoming an in/out battle over Europe. Of course there are sticking points. But to cast the issue as make-or-break is a pernicious nonsense.

There are real questions to be answered as the resolution of the eurozone's problems play out. At this point, however, with so little certainty about what a post-crisis Europe might look like, carping about referendums and clawing back powers from Brussels is both imprudent and crassly ill-timed. Europe is on the brink of a precipice. Britain should be doing all it can to help, not standing well back, shouting for everyone else to do something, and then threatening to cut the rope.