The number of infiltrated political groups has been released by the public inquiry that was set up by British Prime Minister Theresa May, while she was UK home secretary a few years ago, to examine the conductof the police spies since 1968.
The inquiry has found that at least 144 undercover police officers were deployed to spy on political groups, the names of which have not been made public.
However, it is known to include environmental, anti- racist and animal rights groups, left-wing parties and the far right, the Guardian reported.
The campaigners have been pressing the inquiry to publish a list of the groups and the names of the fake identities that were used by the police spies during their covert missions.
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According to the newspaper, the spies developed elaborate false identities, often based on dead children and supported with fake documentation such as driving licencesprovided by the state.
They spent long periods, usually five years, pretending to be political activists while they fed back to their superiors information about the activities of campaigners and the protests that were being organised.
Earlier this week, the UK Home Office confirmed that the public inquiry was now being headed by a new judge, Sir John Mitting.
He replaced Sir Christopher Pitchford, who stepped down after being diagnosed with motor neurone disease.
The inquiry has been delayed as the police are arguing that most of its proceedings should be held in private in order to protect the spies and their techniques.