Workers at a security company in Sussex are threatening legal and industrial action over plans to install satellite tracking devices in their vans.

They condemn it as Big Brother gone crazy because, like the television show, 24-hour surveillance is set to track every move they make.

Union leaders say new legislation allowing employers to monitor staff phone calls, emails and internet use during work time is in danger of undermining employees' right to privacy.

And for workers at ADT Fire and Security, in Portslade, Big Brother's watchful eyes will follow them into their leisure time if plans to install satellite tracking devices in their vans go ahead.

Workers, who use their vehicles in the evenings and at weekends, say the devices cannot be switched off and suspect the company will use them to spy on their everyday lives.

The engineering union AEEU believes the firm could be in breach of the Human Rights Act, the Data Protection Act and employment contracts and is threatening legal and industrial action.

Legislation in the Regulation of Investigatory Powers Act threatens to undermine that protection, allowing both public and private sector employers to record or monitor communications, often without consent.

The draft regulations unveiled by e-commerce and small business minister Patricia Hewitt last month, are being implemented by the Government, despite opposition from union leaders.

Laurie Heselden, TUC campaigns officer for the South-East, said: "Under the Human Rights Act workers have a right to privacy in the workplace.

"However the contradiction between the two pieces of legislation leads to a grey area of doubt which could be a threat to workers. Currently we have a high degree of uncertainty over what is and what is not permissible. Because of this lack of certainty, workers are clearly vulnerable."

Brighton and Hove Council is one major employer which has published a new draft code of practice covering staff use of email, telephone and internet facilities. A spokeswoman said the guidelines were designed to ensure good practice and that employees acted in accordance with the authority's business objectives and values. They should also protect employees and limit opportunities for fraud.

Andy Richards, who chairs the Brighton and Hove branch of Unison, said the draft had already caused concern among members.

He said: "The guidelines issued seem to suggest that almost any use other than for council business could become a disciplinary offence. We don't agree with this. We feel an employee does have a right to privacy even in the workplace. If discipline does happen, we will take it up with the employer."

The Government maintains its new legislation strikes a balance between protecting the privacy of individuals and enabling industry and business to get maximum benefit from new communications technology. Trade unions claim it gives companies a free reign to spy on almost every workplace communication.

The TUC says firms should allow staff reasonable use of personal emails as long as it does not interfere with their work.

It is calling for employers to sit down with trade union reps and agree frameworks that detail permitted use and the degree and nature of monitoring.

And it wants workers to be warned that emails could be scanned for obscene, indecent or racist remarks and told whether their emails could be checked if they are absent or on holiday.

Bill North, secretary of the Trades Council, the umbrella group for all trade unions in Brighton and Hove, agreed that if a company wants to monitor calls to ensure quality control, and prevent misuse of communication systems, it should sit down with trade union reps and draw up a proper code of practice.

He said: "I don't agree with random trawls, looking through on the off-chance it. If a person makes the occasional personal call, not affecting their work, I don't see the problem. Management should have better things to do than snoop on their staff. They wouldn't feel it was acceptable for it to happen to them."