Rolls-Royce Aerospace has fired five people for misuse of internal e-mail as part of an ongoing enquiry about the transmission of "inappropriate material".

Gary Atkins, a Rolls-Royce spokesperson, would not disclose the exact details of what constituted "inappropriate material", but said that material had been introduced from outside, breaching security. He added that the manufacturer has a closed e-mail system with little internet access.

When the security policy violation was discovered 14 staff from across the manufacturer's Bristol site were suspended.

The story, which was leaked to the Bristol Evening Post, highlights a growing problem of e-mail and internet abuse among companies and large organisations.

A survey of senior directors of 800 FTSE-1000 companies, by network security specialist Integralis, revealed that 41 per cent of companies have no clear corporate policy on employee e-mail and internet usage.

The evidence of exposure to 'cyberliabilities' is also revealed in the survey - 15 per cent of directors had already disciplined employees for inappropriate use of the internet.

Common cyberliabilities which employees expose themselves to include charges of racial or sexual discrimination and harassment, libel and misuse of personal information in breach of the Data Protection Act.

The company directors surveyed estimated that up to two hours a day are wasted on personal e-mail communications or surfing the internet, at a cost of £3.9m to UK businesses with 1,000 staff.