One of Germany's most outspoken economists, Hans-Werner Sinn, suggested in an opinion piece in the Financial Times letting euro zone countries leave the currency bloc temporarily to restore their competitiveness with the prospect of rejoining later, Reuters reports.

Sinn, the head of Germany's influential Ifo think tank, does not shrink from controversy and has long called for Greece to leave the euro zone - but he has little influence on policymaking.

"The core idea is to offer exiting countries the status of associated member, allowing them to adopt their own currency temporarily with the option to return to the euro at a later stage," Sinn and Friedrich Sell, professor at Bundeswehr University in Munich, wrote in the FT's print edition on Wednesday.

The two suggested using a mechanism similar to that adopted by countries planning to join the euro, who have to take part in the European exchange rate mechanism II (ERM II) arrangement for at least two years before joining the currency bloc.
 

"This mechanism could be expanded to allow it to harbour, after a transition period, countries leaving the euro zone, too," Sinn and Sell wrote without mentioning Greece.
 

"This proposal to open the currency union has a decisive advantage over either maintaining the status quo or allowing disorderly exits from the euro zone," they said.
 

"It would give the countries affected a realistic, and therefore credible, hope of returning to the euro."