Detective Chief Superintendent Adrian Tudway, who took over the role of national co-ordinator for domestic extremism last week, said more resources are being invested in identifying potential flashpoints.

He said investigators must walk a "tightrope" as they target the small minority willing to break the law and damage the ability of everyone else to make their voices heard.

Speaking ahead of a wave of fresh demonstrations against rising student tuition fees, Mr Tudway said his officers focus on the "fringe" where protest "spills over" into violence and disorder. Asked if more work is being done in the wake of the Millbank rioting to identify those suspected of plotting to commit crime during protests, Mr Tudway replied: "Absolutely."

He said: "It is quite right in our role as Acpo (Association of Chief Police Officers) goalkeeper to watch where the social protests are going and how they are developing and to try, where possible, to identify flashpoints."

Mr Tudway oversees the work of three units tasked with monitoring the activities of groups, from animal rights activists to environmental protesters and other single issue militant groups. The National Public Order Intelligence Unit (NPOIU), National Domestic Extremism team and National Extremism Tactical Co-ordination Unit (NETCU) employ a staff of about 100 with an £8.1 million budget.

The three units will be rebranded and brought under the wing of the Metropolitan Police from their current home at Acpo by next summer. The unit could face a further move to the National Crime Agency (NCA) once it takes over the responsibilities of the Serious Organised Crime Agency (Soca) and other bodies.

The domestic extremism units have come under fire for using often intrusive surveillance tactics to identify hundreds of people who have attended protests before sharing the information with other forces.

Mr Tudway, who has worked as deputy to his predecessor, Assistant Chief Constable Anton Setchell, since January, said intelligence officials do not examine the work of trade or student unions.

The former Met detective said: "We would not look at organisations like that because constitutionally that would be wrong. But what we are obliged to do is where there are crossovers from protest into extreme behaviour, whether public disorder or criminality. If you compare the English position with that across Europe, in most European countries the domestic security service have the remit for this."

The Press Association