The letter goes on to ask how Rolls-Royce can allow individuals to "use the company's facilities" to rob singers of their royalties.

A spokesman for Rolls-Royce strenuously denied the correspondent's claims this week. "Neither Rolls-Royce nor its employee representatives are aware of any such activities at the facility," he said.

Trading Standards officer Jim Potts said a letter to the workforce reminding employees of the penalties for counterfeiting usually helped to nip potential problems in the bud.

And he was confident a firm like Rolls-Royce would act quickly should there be any hint illegal activities may be taking place on its premises.

"Counterfeit issues are often difficult to detect in the workplace," said Mr Potts. "You might get one person who copies a CD for a couple of friends for instance, which while still illegal, is often done in innocence.

"But in some cases, Trading Standards has located some quite sophisticated systems where so many CDs are being copied it has turned into a small commercial operation."

He went on to say Trading Standards were always happy to advise and support managemention issues like this.

"There are strict penalties involved in counterfeiting and fines of up to £20,000 can be imposed, or even a term of imprisonment," said Mr Potts.

The letter was sent to Mr Osborne following his visit to the Rolls-Royce Barnoldswick plant earlier this year.