The arrest of 114 people on suspicion of conspiracy to commit aggravated trespass at Ratcliffe-on-Soar power station, near Nottingham, is extremely worrying and may be regarded as further indication of a style of policing that has developed under this appalling government and is undermining the values and needs of a free society.

The local Labour MP Alan Simpson has today raised concerns about whether the action was proportionate. "The scale of it makes people think we are dealing with a major terrorist incident," he said. "We understand there were 200 officers involved and my instinctive reaction to that is to say, well there must be something to do with plans to blow something up, to commit a major disruption of society. My worry is that what we are talking about, in practice, [is] something much smaller."

Simpson, who is generally regarded as a good thing and is giving up his seat at the next election because he decided that Westminster politics is incapable of listening to the demands for more radical action on the environment, could have gone a lot further. Let us be clear that the people arrested yesterday, who have all now been released on bail, have manifestly not committed any crime of trespass. Second, they possess inalienable rights to assembly and protest. Needless to say the Human Rights Act, which I increasingly view as a well-meaning old dear with fewer teeth that my late Aunt Agnes, does not protect people's rights in these situations and so the police are allowed to get away with a pre-emptive strike. No doubt the Nottingham operation benefited from information provided by forward intelligence teams and the monitoring of people's telephone calls and emails.

How far should this activity go? Earlier this year I linked to a story in which police in Brighton were reported to be filming those leaving a climate change meeting at cafe in the town. There are suggestions that police have planted informers on the inside of environmental organisations. Both are unacceptable in a free society.

All this is of acute importance for climate change campaigners, who Simpson must regard as essential in the drive to find quicker and more fundamental solutions to Britain's record of pollution, but there is another principle here which is of such vital significance that I cannot believe it is not pointed out in every editorial of every quality newspaper. If we allow the police to extend pre-emptive actions from the fight against terrorism into all areas of policing we will end up with a situation where it is enough for the police to suspect someone of merely harbouring intention before making an arrest. As the Independent says this morning, we have good reason to suspect the accounts given by police to justify recent actions. The operation in Nottingham over the weekend should be scrutinised at every level to make sure that we are not, inch by inch, entering a period in which intelligence-gathering operations effectively bring to an end free assembly and protest, and allow the idea that the police can read and prosecute people's intentions.