Human rights group Liberty fears a new police database will be an intrusion into the private lives of hundreds of school children.

It is being used to help teachers identify pupils involved in crime but Liberty says innocent youngsters could be targeted simply because they passed through an area where a crime took place and were spotted on camera.

Liberty is among a growing number of campaigners who fear Britain is turning into a police state where cameras and other surveillance systems pry into people's lives, treating everyone as a suspect.

Police say the database is a valuable tool for tracing criminals and people who have done nothing wrong have nothing to fear.

Sussex Police has built a database to store CCTV pictures of people committing crimes, which will make it easier for them to be identified.

Slide shows will be made from the images and shown to teachers, probation service staff and prison officers to see whether they can identify the suspects.

Liberty is concerned the system could lead to hundreds of pupils being investigated when they have done nothing wrong.

The Suspect Identification and Recognition Database (Sird) has already led to several arrests.

It took nine months to build and was developed by Insp James Asser and the force's IT department. He said: "It has huge potential and we're looking forward to taking it into our communities and identifying those who are wanted for crimes across the whole of Sussex.

"We need the support of our communities and partner agencies. For example we have hundreds of images of young people committing crime and want to go into schools and speak to staff who are more likely to be able to identify them."

Information will be passed to the police in confidence.

So far 400 pictures have been loaded on to the database. The force hopes about 1,000 more will be added every month when it becomes fully operational.

Insp Asser said: "This also sends a clear message to the offenders that if they commit a crime in Sussex they will get put on the database and eventually they will be identified."

Gareth Crossman, of Liberty, said: "Targeted identification is a common and legitimate police technique when used properly. It helps link suspects to specific incidents. Unfortunately, the fact thousands of images are to be used indicates Sussex Police is taking part in 'fishing expeditions'.

"Pupils who have done nothing more than be in the area when a crime is committed are likely to face investigation."

Chris Keates, general secretary of teaching union NASUWT, said teachers had a duty to use the system.

He said: "Teachers like any other citizens must provide any information they have which may help."