The next big computer virus attack in the UK could cost £2.1bn, according to a new report.

Antivirus (AV) company McAfee claims an attack could result in 2.2 million office days lost in downtime.

It says the worst hit will be small and medium-sized enterprises (SMEs) that have failed to ensure they have adequate virus protection.

Despite regular media attention about viruses in recent years, keeping AV protection software up-to-date is widely ignored by SMEs, the report said.

The £2.1bn figure was based on the impact of previous virus attacks on SMEs, McAfee said.

The company estimated that 70 per cent of all SMEs had received a virus, with each losing an average of £843, and 7.2 hours in lost computer time.

Only half of all the report's respondents regularly schedule virus scanning of company computers, it added.