The intelligence squad, which will use information from Special Branch officers and MI5, will compile profiles of protesters and organisations considered to be potentially troublesome.
Among the people to be targeted are campaigners against road building and live animal exports, protesters at industrial disputes, hunt saboteurs and far-right groups. The unit will also draw up action plans that chief constables can introduce to head off potential disorder.
The move follows growing concern among police chiefs that so called eco- warriors are becoming increasingly organised and creating an ever growing threat to public order.
Green and civil rights activists reacted with anger to the disclosure of the new outfit, which is to be called the National Public Order Intelligence Unit. They argued yesterday that civil liberties and the right to peacefully demonstrate were being undermined.
There are also fears that people on legal protests could be listed as troublemakers. The national unit, which is due to be operational by the end of the year, will be based at Scotland Yard. It is expected to be headed by Commander Barry Moss, head of Special Branch.
The new outfit will include three existing police teams. In south-west England an intelligence unit has been monitoring New Age travellers and people who occupy land illegally. While in northern England a small team has been logging details of hunt saboteurs. The Animal Rights National Index, which lists details of protesters, is already based at Scotland Yard.
Assistant Commissioner Anthony Speed of the Metropolitan Police, who chairs the Association of Chief Police Officers' Public Order sub- committee, said: "Experience shows that the same people are involved in demonstrations - whether it's disruption of building works and motorways, runways, live animals for export, or people 'reclaiming' the streets.
"It tends to be the same people who support them and travel around the country. It's about keeping a database on them - identifying the main individuals."
He said that people repeatedly involved in clashes during industrial disputes, such as the miners' strike and the Wapping newspaper picketing, could also be targeted. He also cited the 1995 protests at Shoreham, Dover and Brightlingsea against live animal export to the Continent, which at times result in violent clashes, as suitable areas for scrutiny.
"Special Branch officers at ports where trouble is taking place could use the system to communicate information to chief constables elsewhere."
He added that the unit could also be used to draw up information about National Front members and extreme leftwing activitists who are considered likely to become involved in violence.
"All this information will be useful to chief constables - if you know certain groups are involved in an action you can anticipate greater disorder and violence and plan for it in advance," he said.
Chief constables also want to build up action plans for dealing with eco incidents throughout the country.
Mr Speed gave the example of the police having to remove demonstrators who climbed into trees during protests at road building in the South West. "The information about how the police dealt with that will be useful to other forces," he explained.
Special Branches in forces in England and Wales, which gather intelligence about threats to national security, will contribute information to the unit.
MI5, the Security Service, will also contribute details of individuals they believe to be involved in terrorist activities or serious disorder.
John Callaghan, overseas liaison director for Compassion in World Farming, the pressure group responsible for organising many of the demonstrations at Brightlingsea in Essex and Shoreham in Sussex against the export of veal calves, condemned the extra monitoring of activists.
"This is going to far. We are constantly being videoed by the police - I'm worried as a law abiding person that we are coming under this kind of scrutiny. Peaceful demonstration is part of a democratic society - it is part of our rights."
John Wadham, director of Liberty, the civil rights organisation, argued that the unit would inevitably spend much of its time monitoring peaceful protests. "The problem is, without a right of privacy and a right of protest, there will inadequate controls and regulations," he said.
Ecology and green pressure groups have multiplied in the past few years and have become an increasing headache to the police.
In May the organisation Reclaim The Streets caused serious disruption at the G8 summit in Birmingham and at other times has brought parts of London and Brighton to a standstill.The cost of covering the demonstrations against animal exports on the South Coast was more than pounds 6m.Reuse content