NEW human rights laws could be used to ban the fitting of 'black boxes' on vehicle fleets, amid claims that they allow companies to spy on staff out of hours.

The Amalgamated Engineering and Electrical Union has threatened legal action against ADT Fire and Security, one of the country's biggest security companies, if it fits the software to its vehicles. And civil liberties organisations are backing a challenge, saying that if the devices are used to collect information there could be a breach of the Data Protection Act.

ADT has a fleet of 4,300 vehicles, 1,300 of which are used by service engineers who maintain alarm systems. A spokesman for the AEEU, which represents most of ADT's engineers, said: 'We accept that customers can be given accurate arrival times and increased levels of performance, but there are other ways to ensure this.

'We want to discuss together how we can improve customer care and ensure fuel efficiency is a number one priority for us all. But installing surveillance equipment that you cannot turn off, which will be monitoring people at weekends with their families, is unacceptable.'

James Welch, legal director of Liberty, said: 'We are concerned about the possibility of people being tracked out of office hours. We think it's wrong for employers to obtain information and hold it.'

ADT human resources manager, Arie Vermeulen, said: 'ADT Fire and Security is discussing with the AEEU the use of a vehicle asset management system on our service vehicles in order to give our customers an enhanced level of service. We are unable to make any further comment at this time.'