A comprehensive solution to the euro crisis must have three major components: reform and recapitalisation of the banking system; a eurobond regime; and an exit mechanism.

First, the banking system. The European Union’s Maastricht treaty was designed to deal only with imbalances in the public sector; but excesses in the banking sector have been far worse. The euro’s introduction led to housing booms in countries such as Spain and Ireland. Eurozone banks became among the world’s most over-leveraged, and they remain in need of protection from counterparty risks.

The first step was taken by authorising the European financial stability facility to rescue banks. Now banks’ equity capital levels need to be greatly increased. If an agency is to guarantee banks’ solvency, it must oversee them too. A powerful European banking agency could end the incestuous relationship between banks and regulators, while interfering much less with nations’ sovereignty than dictating their fiscal policies.

Second, Europe needs eurobonds. The introduction of the euro was supposed to reinforce convergence; in fact it created divergences, with widely differing levels of indebtedness and competitiveness. If heavily indebted countries have to pay heavy risk premiums, their debt becomes unsustainable. That is now happening. The solution is obvious: deficit countries must be allowed to refinance their debt on the same terms as surplus countries.

This is best accomplished through eurobonds, which would be jointly guaranteed by all the member states. While the principle is clear, the details will require a lot of work. Which agency would be in charge of issuing, and what rules would it follow? Presumably the eurobonds would be under eurozone finance ministers’ control. The board would constitute the fiscal counterpart of the European Central Bank; it would also be the European counterpart of the International Monetary Fund.

Debate will therefore revolve around voting rights. The ECB operates on the principle of one vote per country; the IMF assigns rights according to capital contributions. Which should prevail? The former could give carte blanche to debtors to run up deficits; the latter might perpetuate a two-speed Europe. Compromise will be necessary.

Because the fate of Europe depends on Germany, and because eurobonds will put Germany’s credit standing at risk, any compromise must put Germany in the driver’s seat. Sadly, Germany has unsound ideas about macroeconomic policy, and it wants Europe to follow its example. But what works for Germany cannot work for the rest of Europe: no country can run a chronic trade surplus without others running deficits. Germany must agree to rules by which others can also abide.

These rules must provide for a gradual reduction in indebtedness. They must also allow countries with high unemployment, such as Spain, to run budget deficits. Rules involving targets for cyclically adjusted deficits can accomplish both goals. Importantly, they must remain open to review and improvement.

Bruegel, the Brussels-based think-tank, has proposed that eurobonds constitute 60 per cent of eurozone members’ outstanding external debt. But given the high risk premiums prevailing in Europe, this percentage is too low for a level playing field. In my view, new issues should be entirely in eurobonds, up to a limit set by the board. The higher the volume of eurobonds a country seeks to issue, the more severe the conditions the board would impose. The board should be able to impose its will, because denying the right to issue additional eurobonds ought to be a powerful deterrent.

This leads directly to the third unsolved problem: what happens if a country is unwilling or unable to keep within agreed conditions? Inability to issue eurobonds could then result in a disorderly default or devaluation. In the absence of an exit mechanism, this could be catastrophic. A deterrent that is too dangerous to invoke lacks credibility.

Greece constitutes a cautionary example, and much depends on how its crisis plays out. It might be possible to devise an orderly exit for a small country like Greece that would not be applicable to a large one like Italy. In the absence of an orderly exit, the regime would have to carry sanctions from which there is no escape – something like a European finance ministry that has political as well as financial legitimacy. That could emerge only from a profound rethinking of the euro that is so badly needed (particularly in Germany).

Financial markets might not offer the respite necessary to put the new arrangements in place. Under continued market pressure, the European Council might have to find a stopgap arrangement to avoid a calamity. It could authorise the ECB to lend to governments that cannot borrow until a eurobond regime is introduced. But only one thing is certain: these three problems must be resolved if the euro is to be a viable currency.