Scotland is emerging as a major centre for counterfeit computer software, according to the world's largest software company.

Microsoft has revealed that 20,000 labels which are used to prove the authenticity of software were stolen in Glasgow in April.

Those labels will now be used by software counterfeiters to make it virtually impossible for consumers to tell real and fake products apart.

Experts have suggested the stolen labels could possibly be worth as much as �1m on the black market.

Microsoft is a frequent target for pirates

Microsoft has already been the target of computer criminals in Scotland.

In 1997, thieves stole software worth about �10m from a factory in East Kilbride which was licensed to make Microsoft products.

During that raid, which saw two security guards tied up, about 200,000 certificates of authenticity (Coa labels) were also stolen.

Jim McNulty, the firm's investigator in Scotland, said: "Coa labels have become very valuable items to software counterfeiters.

"They will apply them to a counterfeit product rather than a genuine product and this has the effect of the persuading the buyer that the software is genuine when it is in fact counterfeit."

Increasing numbers of people are being taken in by counterfeit software because of the difficulty of spotting it.

Clackmannanshire Council bought fake product licences by mistake two years ago. The council had to pay Microsoft �150,000 for new licences and to cover legal costs.

Of the 20,000 labels stolen from Glasgow, just 5,000 have been recovered by police and Microsoft investigators.