Eurojust, the European Union's judicial co-operation unit, said on its website that it was ready to offer support to member states' law enforcement authorities to monitor the use of internet telephony systems (VoIP) such as Skype.

The EUObserver quoted Eurojust spokesperson Joannes Thuy as saying that the "closer watch" would not affect "regular users" but rather was directed towards criminal structures and individuals. Preliminary talks with each member prosecutor-general's office and police could take some time, meaning that it could be several months before steps were taken.

The idea is the brainchild of anti-mafia Italian prosecutors. Police in Milan have said that crimes including weapons and drug trafficking and running of prostitution rings were all co-ordinated through Skype. This made it difficult for authorities to track calls because practice was for police to tap landlines and mobile phones in investigations.

According to Eurojust, Skype was refusing to share its secret encryption system with authorities.

"Skype co-operates with law enforcement where legally and technically possible. Skype remains interested in working with Eurojust despite the fact that they chose not to contact us before issuing this inaccurate report," Brian O’Shaughnessy, head of corporate communications at Skype, said in a statement, as quoted by EUObserver.

EUObserver said Bavarian authorities had tried to track a Skype conversation and even had hired an IT firm to do so, but with no success.

Skype was developed by Estonian programmers working for a Danish-Swedish business. In 2005, it was sold to E-Bay and now has more than 350 million users around the world.