One of the architects of the euro, former European Central Bank chief economist Ottmar Issing, has suggested that if the single currency is to survive some of its current members would have to leave the eurozone.

“The euro itself does not need to be saved. What has to be saved is the stability of the euro and the euro area. The question – how many countries can participate, this is the challenge with which Europe is confronted,” Issing said in an interview with CNBC.

He said the euro had accepted too many members when it was launched more than a decade ago.

“We should have started with a smaller number, no doubt about that, with stricter rules. But this is spilled milk. Now we have this composition, and the idea that we should have a policy that no country ever should leave is something which is an invitation to blackmail,” he said.

Issing also rebuffed claims that the ECB should be doing more to tackle the euro crisis and said that the mutualisation of debt “must not happen.”

“A break up of the euro area would be a major disaster but the alternative to that, being a monetary union in which the reputation of the ECB would be undermined, or even destroyed. The euro would tumble and governments would pile up debts without any limit. I think this is a scenario – a horror scenario – which comes close to the disaster of a break up,” he said.