One in three people is being monitored at work, including many who are now based at home, new research suggests.
Prospect said its study among 2,400 workers shows new protections are needed because of the increase in employer surveillance.
Around one in seven people working from home are being monitored by cameras, compared with one in 20 earlier this year, said the union.
Four out of five respondents said the use of webcams to monitor remote workers should either be banned or heavily regulated.
Only 8% of those surveyed believe employers should be allowed to decide unilaterally when to use cameras to monitor people working in their own homes.
The finding comes as the Information Commissioner’s Office (ICO) is reviewing guidance to employers on the use of new technologies such as monitoring.
Workers aged 18 to 34 are more likely to be monitored than their older colleagues, said Prospect.
Prospect is calling for a range of measures to protect employees from intrusive monitoring, saying workers should always be consulted on how technology is being used.
The union has also called for the Government to consider banning the use of camera monitoring in people’s homes, making it illegal for employers to use webcams to check up on workers outside of meetings and calls.
Prospect general secretary Mike Clancy said: “We are used to the idea of employers checking up on workers, but when people are working in their own homes this assumes a whole new dimension.
“New technology allows employers to have a constant window into their employees’ homes, and the use of the technology is largely unregulated by Government.
“We think that we need to upgrade the law to protect the privacy of workers and set reasonable limits on the use of this snooping technology, and the public overwhelmingly agree with us.”
Shadow digital minister Chi Onwurah said: “This deeply worrying research shows just how anxious many people are about the use of invasive surveillance whilst they work.
“Ministers must urgently provide better regulatory oversight of online surveillance software to ensure people have the right to privacy, whether in their workplace or home.
“The bottom line is that workers should not be subject to digital surveillance without their informed consent, and there should be clear rules, rights and expectations for both businesses and workers.”
An ICO spokesman said: “People expect that they can keep their personal lives private and that they are also entitled to a degree of privacy in the workplace.
“If organisations wish to monitor their employees, they should be clear about its purpose and that it brings real benefits. Organisations also need to make employees aware of the nature, extent and reasons for any monitoring.
“We are currently working on updating our employment practices guidance to address the changes in data protection law and to reflect the new ways employers use technology and interact with staff.”