All environmental protesters attending the Climate Camp demonstrations today will be photographed by police, although organisers have told activists that they do not need to co-operate by showing their faces.

Senior officers said the tactic of recording images of those taking part in high-profile demonstrations would continue, with members of so-called Forward Information Teams being present at the six initial meeting points and the final secret camp destination, once it is identified.

Campers have been warned to watch out for police photographers, and are expected to respond by blocking their views with placards and banners and taking pictures of the photographers themselves.

The demonstrations will be the first test of public order policing since the G20 protests, when the Met was criticised for its heavy-handed tactics. Police have signalled a change in approach since the April demonstrations, which resulted in the death of Ian Tomlinson, but are to continue filming and photographing those attending. A third of the public believe filming protesters is an invasion of privacy, according to a YouGov poll of 2,000 people published yesterday.

Chief Superintendent Helen Ball, of the Metropolitan police, said taking photographs of protesters remained an important tactic.

She said police would also stop and search anyone they were suspicious of, but it is likely any such actions will be kept low key.

Ball said: "At the moment we will be photographing people on arrival at the camp because it is important for us to know if there are people coming who want to cause violence and disorder.

"We will not be routinely stopping and searching everybody going into the camp and we have briefed officers carefully on searching people and what the spirit of the operation is."

Police have made a last-minute plea for organisers to tell them where the camp will take place.

"We are putting in a neighbourhood policing team for the periphery of the camp and for the local community.

"But we have not been able to go further than that because we do not know where it is going to be."

Up to 30 officers based at the Met's Lambeth control room will oversee developments at the Climate Camp via a network of CCTV cameras.

Operators have access to more than 12,000 cameras across the capital, plus live feeds from the force's three helicopters.

Senior officers have split control-room operators into teams, watching different parts of London, until the final campsite is identified.

The control room will be packed with up to 150 people at the weekend, as the force oversees the Notting Hill carnival, its biggest annual policing event.

About 200 extra officers have been drafted in from five forces - Gwent, Cheshire, North Wales, West Mercia and City of London - to bolster numbers at the camp.

The police operation, dubbed Operation Bentham, is in the spotlight after angry clashes marred demonstrations during the April G20 meeting of world leaders in London.

The force will use a mobile police station, helicopter-mounted loudhailer and Twitter account to improve links with protesters.