Big Brother is keeping tabs on satnav motorists

The controversial scheme is built into the small print of a contract between the Department for Transport and the satnav company Trafficmaster.

Currently the 'spy in the sky' system is limited to some 50,000 drivers who have Trafficmaster's Smartnav system.

However, the system could provide the blueprint to monitor the location, speed and journey details of millions of drivers in years to come.

Such a system might be used to manage a system of road pricing, where motorists are charged according to which roads they use and the time of day. It might also be used to identify speeding drivers.

It could also be used by everyone from the police to the taxman to discover whether an individual is

where they claim to have been at any point in time.

The Daily Mail has seen details of the £3million contract. The partnership, which began in July, is described by the DfT and the company as necessary to monitor traffic flows and congestion blackspots.

However, the small print makes clear that the information being collected and handed over to the Government is far more detailed and, potentially, sinister.

The document states: "The unprocessed data to be supplied - by Trafficmaster - will consist of individual vehicle location reports and associated information."

It then gives an example of what this 'associated information' is together with how it should be collated and presented.

This includes a unique number identifying the vehicle, two six-figure Ordnance Survey readings for the location, and the date and time when the information was captured. It also includes what kind of vehicle it is, the speed it is travelling and the direction.

A snapshot of this information is collected at 15-minute intervals and then collated and provided in its raw form to the DfT. A Trafficmaster spokesman said: 'Our responsibility is to provide the data. It is not necessarily our responsibility or decision as to how it is used.'

The revelations will fuel concerns that Britain is turning into a surveillance society.

However, the DfT stressed that all the information is anonymised to ensure they do not have the personal details of drivers.

A spokesman said: "This contract provides anonymous data about sections of journeys made so we have a good understanding of where and when congestion is forming. Without fully understanding the effects of congestion we cannot develop ways of tackling it.

"We have no interest in knowing where people are travelling to and from."