It is hard not to have the gravest of forebodings about the European and British economies, and about the future of Europe itself. Nobody would start from here – an ill-designed single currency interacting with an insupportable burden of private debt created by oversized, undercapitalised banks. And it's as much a problem in the US and China as in Europe. There are only least bad ways forward: none good. This is a crisis in contemporary capitalism as much as a crisis of Europe's monetary regime and governance. It needs to be seen in those terms.

But so saturated is British commentary in jingoistic Euro-scepticism that Europe's travails are portrayed as proof positive that it is European visionary delusions rather than contemporary capitalism that is at fault. Greece, and indeed Ireland and even Italy, are urged to get out of the euro, for the euro to be smashed and for the entire EU project to be abandoned. This is the route to prosperity and wellbeing – with no trace of self knowledge as British trade performance deteriorates even after a monumental devaluation while our economy is still years away from recovering to 2008 levels of peak output. That is Europe's fault, or so runs the line – not the fault of our dysfunctional economic structures and policies.

However, Britain's interest is unambiguous: it lies in the survival of the euro. There is too much easy talk about countries leaving. Last week, financial policy committee member Robert Jenkins spelled out the consequences for Britain and for Europe of Greece now quitting the euro. There would be seismic bank runs in Ireland, Portugal, Spain and even Italy as citizens and companies, fearing the same could happen to them, moved their cash out of their countries. Weaker banks, tottering from losses in Greece, would fold. The European Central Bank would be overwhelmed. The European economy would slump – and Britain with it.

Greece's fight is our own. But what is being asked of Greece's new interim prime minister, Lucas Papademos, is impossible. Unemployment is 18.4%. The schedule of its foreign loan repayments over the next five years beggars belief. On the other hand, Greek capitalism, a network of family oligarchs rigging Greek markets and leading a society in which tax evasion is morally and socially acceptable, is in acute need of reform. Europe could have been organised around floating exchange rates rather than a single currency, but the vast overhang of private debt alongside crocked banks demands similar medicine.

And while staying in the euro is in the interest of Greece – and Italy – it is in the rest of Europe's interest too. But there has to be a quid pro quo for all the pain that such severe austerity involves. Private and public debt needs to be radically lowered; and in a world of little growth there are only two routes. Either it has to be forgiven by their creditors, or there has to be inflation. If the eurozone can deliver neither, its future is in question.

In July and, again, in October, the EU signalled it understood what needed to be done and moved towards it – a combination of decisive debt forgiveness, the creation of a European Monetary Fund, substantially financed by Germany and which could bail out stricken banks and even governments, and the empowerment of the European Central Bank to go beyond supplying emergency cash on crisis terms. Instead, it could act as a lender of last resort everywhere in the eurozone.

The system could potentially be put in place fast; the right sentiments have been uttered – but after each summit Germany has consistently blocked making the money flow. It has said no to the European Central Bank operating as a lender of last resort across the eurozone; no to creating a genuine European Monetary Fund on the scale needed; no to the creation of single euro bonds. Ireland, Greece and Italy are all doing their part. Germany must now do its – or the euro will buckle.

Germany's phobias are well-known – inflation and then slump led to Hitler. What's more, the German constitutional court has ruled that the EU is a Staatenbund (a group of states). This means that Germany can only constitutionally make fiscal transfers to other members if each one is agreed by the German parliament. But phobias and constitutional courts cannot trump the agonising choice facing Germany and Europe.

Germany profits richly from the way the eurozone is organised. It is the only country in Europe whose share of world trade has risen over the past 10 years. But it enjoys the same exchange rate as much weaker exporters such as Greece or Spain – a huge boon. Even Britain, with our much vaunted floating exchange rate, has seen our share of world trade fall by a third over the same period.

Germany now has to accept its part of the bargain. The choice must be confronted. One option to secure the euro's future is via widespread debt forgiveness and fiscal transfers backed by Germany; the only other route out is inflation.

Here I make a modest proposal. Instead of delivering purposeless lectures from the sidelines about the need for action while he prepares to blame Europe for the ongoing British stagnation, for which he is primarily responsible, David Cameron should make the intervention of his life. He should travel to Germany and make a speech in German – however embarrassing – spelling out the choices. If Germany is unprepared to accept them, he should argue that the least bad option is not for Greece to leave the euro – but for Germany, whose economy is strong enough to take the shock, to do so.

He should say that while it was right for Britain not to join the single currency as it was previously constructed, if Germany were to act responsibly, Britain would peg sterling to a reformed euro and in the long run even consider joining the regime. Moreover, Britain would do this either way, he could argue – eventually joining a single currency in which Germany accepted its responsibilities or a single currency without Germany.

Such a speech – which, of course, will never be made – would create turmoil in Germany. It fears isolation in Europe even more than it fears inflation. It prizes the undervaluation of its exports priced in euro. It would force its leadership to recognise that there are other potential ways of organising our continent other than around German preoccupations – and perhaps trigger the change in German policy that is needed. It would change the rules of the game at a stroke, and show that Britain is a European force with which to be reckoned. But Cameron is trapped into Little England isolationism. And Little Englanders, along with moralistic and blinkered Germans, threaten to sink both the idea of Europe – and its economy.