A fifth of all messages received by corporate email servers are spam, according to research by an antivirus company.

Panda Software said that its GateDefender Performa website had identified 21 per cent of emails as spam messages. 

Perhaps more worrying, Panda found that one in 20 emails were infected with malware.

Statistics based on staff browsing also found that almost 40 per cent of internet use in companies is non-work related.

Personal use of the internet accounted for almost an hour of employees' time every day, which in 2005 resulted in losses of more than €300,000m.

"Use of adequate security devices is fundamental in order to mitigate this situation," said a statement by Panda.

"They not only offer excellent protection against internet threats and inappropriate use of the web, but ensure a rapid return on investment."