Police have raided dozens of homes across the country as they questioned climate change protesters planning action this summer against coal-fired power stations and airports.

More than 200 officers carried out a pre-emptive raid early on Monday, arresting 114 people thought to be preparing a protest at the Ratcliffe-on-Soar power station in Nottinghamshire.

Yesterday it emerged that as the campaigners were in custody, officers raided homes around the UK, seizing computer equipment and mobile phone records.

All of those arrested but not charged for conspiracy to commit criminal damage and aggravated trespass were released yesterday on police bail – many with onerous conditions, including bans on approaching any UK power station or attempting to disrupt their operations.

Campaigners said this was an attempt to reduce numbers at major climate camps and demonstrations planned over the summer and to limit protests if the government decides to go ahead with a major new coal-fired power station at Kingsnorth in Kent.

A spokesman for Nottinghamshire police said specialist equipment, including bolt cutters and chains, that was seized during the raid suggesting that the protesters posed a "serious threat to the safe running of the site".

However the mass raids and the lack of charges prompted renewed concern about the tactics of officers policing environmental protests.

Shona Jainjuah, from the Camp for Climate Action, which yesterday denied planning the action, said: "First the police violently attack the climate camp during the G20, and now 114 people are arrested before they have actually done anything. People should be very concerned about how the police are stepping over the line in the way they are targeting activists."

An activist who did not want to be named added: "This is an attempt to silence a peaceful movement of young people trying to make people aware of the greatest threat to the world. This is madness."

Senior figures in the environment movement said surveillance of activists now regularly went beyond demonstrations to include open public meetings, campaigners' offices and individual activists.

John Sauven, executive director of Greenpeace UK, which also denied any involvement in the action, said police were filming people arriving at and leaving the group's London headquarters, and had stopped and questioned members leaving public meetings about opposition to the expansion of Stansted airport.

"These are all quite legitimate activities so we can see from what's happening that the level of police surveillance is increasing dramatically, coupled with which is the big increase in technology at their disposal to monitor people," said Sauven, citing the example of CCTV cameras that can be used to track vehicles and equipment to pinpoint mobile phone users.

It emerged yesterday that police almost certainly used a mole in the fast-growing climate movement to warn them of the impending action and to locate the activists.

According to E.On, the owners of the Ratcliffe power station, energy companies across the region had been warned days in advance of a possible major action, and had been advised to increase their security over the weekend.

"We got the heads up a few days before that there was the potential for there to be a greater risk of protest, not just for Ratcliffe but for other stations in the north and Midlands", said a spokeswomen for E.On.

"Police who arrested us told us that they had known about the action at least a week before," said one protester who was arrested yesterday morning. "They were waiting for us. It's difficult not to conclude that there was a mole."

Police have infiltrated Greenpeace and other activist groups for some time, and the rapid growth of the climate change movement, with people new people joining every week, has made it easier.

Only a small handful of people are likely to have known where or what the Nottinghamshire action was to be, with everyone else being told by word of mouth to meet at a prearranged time and place.

Activists are asked to leave their mobile phones at home and to make no calls in advance, but police have the technology to track people to within a few metres.

"The size of the police operation and the early warnings both suggest the police had inside information," said one woman arrested.