When you are in a radical movement, it’s wise to assume that the person arguing for the most extreme action is an agent provocateur. The question for opponents of fracking is on whose behalf are the agents provocateurs provoking.

Nato and the Romanian and Lithuanian governments have alleged that Russia is urging on opponents of the new technology. Not because Putin gives a damn about global warming, but because he wants Europe to remain dependent on Russian gas. They have no conclusive proof. But the prominence the Kremlin’s apparatchik journalists on RT, the state-funded television channel, give to fracking protests suggests Russian agents may be seeking to manipulate the green movement.

The naive might suppose that the British authorities would not want to be Putin’s mirror image and would allow the argument on the future of energy policy to proceed without interference from the cops. Not so. Last week, Canterbury’s Christ Church University revealed that the Kent constabulary had demanded the names of everyone at a debate on fracking. The university is a respectable institution. Its panel included geologists, councillors and engineers. Perhaps their friends and families know something I don’t, but they looked like respectable citizens too.

But the police insisted on knowing the identities of everyone in the hall. When the university refused to co-operate, Kent police sent a chief inspector to observe the meeting as an “interested stakeholder”. It did not explain what interest a police “stakeholder” had in debates on climate change, beyond an interest in spying on the participants.

Stuart Jeffery, a Green party candidate in the audience, made the essential point that people will be frightened of engaging in the normal arguments of a democracy if the police are taking down their names. He has every reason to be suspicious. Kent Greens are still recovering from the news that the police had logged 22 meetings organised by one of their councillors, Ian Driver. Detectives marked him as a clear and present danger because he organised protests against animal exports (a cause dear to grey-haired cat lovers everywhere) and in favour of gay marriage (a cause so subversive David Cameron’s Conservative-led coalition took it up and passed it into law).

I am the first to put down people who say democracies are police states as pampered hysterics, so lost in self-important dreams of victimhood they do not understand the sufferings of the subjects of dictatorships. But I and, I hope, anyone else who uses this argument must accept that the reason why we are not a police state is because citizens have fought for centuries to limit police powers. They may have been hysterical on occasion. Their critics may have been able to say that they were fools who did not understand that life here wasn’t so bad when compared to the tsarist empire, Nazi Germany or the Soviet Union. The fact remains that what freedom we have depends on our willingness to fight for it.

If you want to know why the right to protest needs defending, read Undercover, by my Guardian colleagues Rob Evans and Paul Lewis, one of the most important pieces of investigative journalism in years. Evans and Lewis showed how from 1968 the Metropolitan police’s special demonstrations squad sent “deep swimmers” into radical organisations. They adopted new identities and convinced activists that they were friends, comrades, lovers and worthy fathers of their children.

Bob Lambert, to take the most ghoulish case, groomed an animal rights protester. As part of his role playing, he got her pregnant and then abandoned her and their infant son when she was no longer of use. Under the protection of parliamentary privilege, the Green MP Caroline Lucas accused Lambert of leaving a firebomb in a department store while he was posing as an agitator. Lambert denied it, but added: “It was necessary to create the false impression that I was a committed animal rights extremist to gain intelligence.”

He went beyond creating “false impressions” and fathering children he planned to dump. He acted as a classic agent provocateur by co-writing the leaflet that led to McDonald’s suing the environmental activists Helen Steel and David Morris. As Steel and Morris fought for their right to say that McDonald’s junk food was indeed junk, they found themselves trapped in the longest libel trial – indeed, the longest trial full stop – in British history. I am still astonished by the absence of astonishment that a cause celebre, which made the British legal system a laughing stock, was the result in part of a police dirty trick.

There are grounds for believing that Lambert carried on as a provocateur when he went on to run the Met’s Muslim contact unit after 9/11. He allied with the Muslim Brotherhood and other elements on the Islamist right. As the neoconservative writer Douglas Murray noticed this month, he secured their confidence by presenting “a small number of people, including me, as cold war-style enemies of Islam” – a dangerous charge to throw at anyone in fanatical times. Murray wants to know if Lambert was trying “to smoke out radicals by using me and others as bait”. If you believe the official line, the black ops have stopped and thus there cannot be “deep swimmers” in today’s anti-fracking movement urging it to be ever more extreme in the hope of discrediting its cause. All is well with our democracy. There’s no need now for comparisons with Russia.

But consider what little we are allowed to know about police contempt for fundamental liberties. Kent police – yet – again seized thousands of confidential phone records from the Mail on Sunday without a warrant from a judge, and in defiance of the law’s presumption that journalists’ sources should be protected. Meanwhile, the security establishment has not disowned Lambert. John Grieve, a former head of the Met’s criminal intelligence branch, gave him an academic post at London Metropolitan University where he instructs graduates on how to be police officers, a task for which he is uniquely unqualified.

I favour fracking, in part because gas-fired power stations are less damaging to the atmosphere than their coal-fired equivalents and in part because I do not want Britain to be dependent on Saudi Arabia, Russia or any of the other petro-dictatorships when the price of oil rises again.

I accept I may be wrong. Even if I am not, the environmental and geopolitical costs of fracking need to be debated without fear of police spies and dirty tricks. As it stands, the sinister behaviour of the police threatens to make a free, fearless and necessary debate impossible.