Extinction Rebellion (XR) should be treated as an extremist anarchist group and police must stop their “soft touch” approach, a former Scotland Yard head of counter-terrorism has warned.

Richard Walton, who headed the Met’s Counter Terrorism Command until 2016, said his investigation into XR revealed it had a “subversive” agenda rooted in the “political extremism of anarchism” rather than just campaigning on climate change.

He said he had uncovered evidence that XR leaders advocated “revolution” to overturn capitalism, mass protest and law-breaking aimed at achieving a breakdown of democracy and the state - an intent many of its middle class and celebrity backers appeared unaware of.

His 73-page report, to be published on Wednesday by think tank Policy Exchange, criticised Scotland Yard for its “passive” and “tolerant” response to XR’s London protests in April which caused gridlock at a cost of at least £28 million in lost shop takings and extra policing.

He recommended police adopt a “proactive” approach to prevent XR and other political activists embarking on illegal tactics.