'Big Brother'-style IT systems are now watching half of the UK's employees, fuelling fear and stress in the workplace.
More than 12 million people are scrutinised by electronic surveillance at work causing a sharp rise in stress levels, according to a survey by the Policy Studies Institute (PSI).
For 23 percent of UK employees, these IT systems are used to check the quality of work produced. Feelings of exhaustion and anxiety related to work are 7.5 percent higher among these 23 percent.
Privacy advocates say the surge in cyber-snooping by bosses will land an increasing number of employers in court defending breaches of the Human Rights Act.
Last year a college secretary from Wales represented by human rights group Liberty won a legal battle against her employers after her personal communications were monitored for 18 months without her consent.
Simon Davies, director of Privacy International, told ZDNet.co.uk's sister site silicon.com that the 50 percent figure is a "crucial landmark" in the workplace.
He said: "The Data Protection Act offers woeful protection for employees and I would call on the government to present greater protections. I guarantee that we will see more and more human rights cases as this surveillance increases. Surveillance has serious health implications and the government has ignored this."
Michael White, one of the report's authors and research fellow at the PSI, said: "The immediate problem is likely to be a high level of job turnover and increased work strain is associated with adverse health implications. There is certainly the potential that employers could be facing more challenges."
Speaking at the time of their legal victory for the college secretary, Liberty's legal director James Welch said: "Employees don't leave their personal privacy at the front door when they come to work each day. This judgment makes perfectly clear that employers who spy on their staff are infringing their privacy."
Monitoring noted by the PSI study includes logging emails and internet usage, keystroke loggers, recording and timing calls and measuring shop-till throughput.
Bearing the brunt of the IT scrutiny are administrative and white-collar employees, such as call-centre staff and data-entry workers, who complained of an increase in work strain of 10 percent when they are being watched.
But an increasing number of semi-skilled and manual workers, such as production line and distribution workers are also under the electronic eye, similarly reporting an increase in work strain of eight per cent when under scrutiny.
IT monitoring also applies to many managers and professionals but the study, funded by the Economic and Social Research Council, found no adverse effects for this group.