Businesses have been warned about excessively snooping into their workers’ activities and to make sure that any surveillance is legal, transparent and fair.

New guidance issued to companies by the data watchdog states that while some monitoring of staff is allowed, it should not be so heavy-handed that it invades their privacy.

The Information Commissioner’s Office found that a rise in working from home and the development of new technologies meant that 19 per cent of people feared they had been spied on while doing their job.

Of these, 40 per cent believed they had had their timekeeping checked, while 25 per cent thought their calls, emails and messages had been looked at and 15 per cent believed they had been recorded using film or audio.

Employers are allowed to use CCTV, to undertake drug-testing and bag searches and to review a worker’s emails and the websites they look at.

For companies worried about staff productivity, there are also specialist services that allow work tracking, for example by looking at mouse and keyboard movements. However, the regulator said that companies needed to tell staff why they were being monitored and to what extent, to make sure that they were using the least intrusive method to achieve the stated goal, to provide staff with any information they had collected and to keep only relevant data on file.

Emily Keaney, its deputy commissioner of regulatory policy, said: “Our research shows that monitoring at work is a . . . cause for concern, particularly with the rise of flexible working. Nobody wants to feel like their privacy is at risk, especially in their own home. If not conducted lawfully, monitoring can have a negative impact on an employee’s wellbeing and can worsen the power dynamics . . . in the workplace. We want people to be aware of their rights under data protection law.”

Fifty-seven per cent of those surveyed said they would feel uncomfortable taking a new job if their boss was monitoring them. The regulator revealed a generational divide in attitudes towards monitoring, with 26 per cent of those aged 18 to 24 being relaxed about it, compared with 14 per cent of over-55s.

Keaney said: “We are urging all organisations to consider both their legal obligations and their workers’ rights before any monitoring is implemented. While data protection law does not prevent monitoring, our guidance is clear that it must be necessary, proportionate and respect the rights and freedoms of workers. We will take action if we believe people’s privacy is being threatened.”