At least 1,700 employees have been sacked or disciplined for internet or email misuse, including surfing social networking sites, in the past three years.
The figures - obtained from 65 institutions - show how strongly employers are clamping down on staff who spend hours on social networking sites such as Facebook, MySpace and Bebo.
According to a report by The Guardian newspaper, studies have shown that up to £130m a day in productivity is lost because of social networking sites, with Facebook's British members spending an average of 143 minutes a month logged in.
Other common offences include excessive use of other websites or email, viewing inappropriate material such as pornography and the forwarding of offensive emails. An increasing number of employers now attempt to ban sites they consider inappropriate.
Government departments have been among the most unforgiving, continues the report. The Ministry of Justice, formally the Department for Constitutional Affairs, dismissed 30 employees while the Department for Work and Pensions reprimanded 313.
The Metropolitan police disciplined 187 staff, while Hertfordshire police gave formal warnings to 25 after an offensive video clip was circulated.
However, Cary Cooper, a professor of organisational psychology and health at Lancaster University, said that managers should be realistic. "Britain has some of the longest working hours in the developed world. Employers have created this culture. It is natural for people to have to use work computers for organising their personal life."
