A report by the Her Majesty's Inspectorate of Constabulary (HMIC) has found that the undercover policeman, Mark Kennedy, whose actions led to the collapse of a trial of environmental protesters, had "defied" management instructions and was inadequately supervised.
Environmental activist Ben Stewart was one of the defendants in the Ratcliffe-on-Soar case whose conviction was overturned.
He told the Today programme's James Naughtie that the public would not have believed the "abuses of power" committed by undercover officers under the control of senior police had they not been reported in the media.
He called for a public inquiry to look at all the issues surrounding covert operations such as lying in court and said that for a period of time, undercover policing was "largely out of control".
When asked whether he thought it was ever justified for a police force to send undercover officers in to gain information to protect the public, Mr Stewart said it is right to have a unit of "brave" undercover police but they should be "stopping bombs going off and saving lives".
He pointed out that Mark Kennedy's deployment did not result "in a single conviction" and individual operations like the infiltration of a group such as the "Rebel Clown Army" were costing taxpayers £250,000.
He went on to explain that there was a disparity over who is deemed as an extremist in the eyes of the law which amounted to "political prejudice".
Responding to the review Bob Quick, former Assistant Commissioner at the Metropolitan Police, said it welcomed the "balance" struck in the HMIC report because it recognises that there is a threat from protest groups.
He insisted that undercover policing was an "extremely valuable tool" for the police but recognised that "in very few cases, things can go wrong".
Mr Quick added there is a "delicate balance" between civil liberties and the police identifying crime and stopping it and admitted that "a rogue officer has created enormous damage to the reputation of undercover officers".
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