By Patrick Bartlett Europe business correspondent

Polish police have broken up a major counterfeiting operation suspected of circulating fake euro banknotes worth about 1.5m euros.

It is the biggest success against euro counterfeiters since the currency's launch just over a year ago.

Poland, where the gang was based, is not yet a member of the European Union.

A spokesman for the European Central Bank said some of the fake notes had already been found in circulation in euro member countries.

The imitations were of unusually good quality.

Joint operation

Polish police seized a large quantity of the fakes during a raid on a makeshift factory near Warsaw.

As well as a complete counterfeit production line, they secured printing and computer equipment.

The breakthrough was the result of a joint operation between Polish and German police.

So far, six of the 12 alleged gang members arrested - 10 Poles and two Ukrainians - have been charged.

The seizure confirms the ECB's long-held fear that counterfeit gangs would use bases outside the 12-nation eurozone.

Numerous security features make euro notes and coins possibly the best protected currency in the world.

Initial attempts to produce fake notes were of poor quality and easily detectable.

But, to the concern of the banking authorities in Frankfurt, counterfeiters are now managing to produce much more convincing copies.