An undercover policeman who infiltrated a group of environmental activists has revealed how his life has become a "living nightmare" after the operation was exposed, making him feel suicidal.
Father-of-two Mark Kennedy, who spent seven years posing as a green protester before fleeing to the United States for fear of his safety, said his son had told him he never wants to see him again.
Mr Kennedy's double life was uncovered last week when prosecutors dropped charges against six people, accused of planning to invade Ratcliffe-on-Soar power station in Nottinghamshire.
The protesters' legal team claimed the 1m Nottingham Crown Court trial collapsed after Mr Kennedy, a Metropolitan Police officer who used the alias Mark Stone, offered to give evidence on their behalf.
A few days later, it emerged that a second police officer had posed as an activist in Yorkshire, living in Leeds for four years and apparently playing a crucial role in preparations for a demonstration at Drax power station, near Selby.
In his first extensive interview after his undercover role was exposed, Mr Kennedy said he believed that at least 15 others had infiltrated the environmental protest movement.
He said he was involved in five major protests, starting with one at the G8 summit at Gleneagles in 2005 when he passed on "invaluable" information to police about demonstrators' movements.
He said it was passed straight to Tony Blair and that he was given a commendation for his role.
Mr Kennedy claimed he suffered head injuries, a prolapsed disc and a broken finger at a 2006 protest at Drax when he was beaten by five police officers after he tried to stop them hitting a female activist he knew.
He said he also took part in demonstrations at Didcot Power Station in Oxfordshire in 2006, the G20 summit in London in 2008 and in Copenhagen, Denmark.
Mr Kennedy became involved in a sexual relationship during his time undercover, having separated from his wife in 2000.
He said the fall-out from the operation had made him feel suicidal and had devastated his 12-year-old son and 10-year-old daughter.
"I am physically and mentally exhausted," he said. "I have had some dark thoughts. I thought I could end this very quickly.
"I went to see a psychiatrist recently and told her I was having thoughts of suicide.
"I don't have any confidence. My world has been destroyed."
Mr Kennedy said he became estranged from his wife and "had no other friends" during the operation.
"My life was undercover," he said. "Of course I cared about them. But I didn't go rogue.
"I was immersing myself in the culture to do my job, to be credible."
He also spoke of his despair at being confronted by the environmental activists when his girlfriend discovered his passport in his real name.
Mr Kennedy said the atmosphere at the meeting was "hugely menacing" as he was told his former friends knew the full details of his true identity.
He said: "I danced around it in circles for about four hours. It was exhausting. I cried a lot.
"It was the end of my tether. They broke me.
"An hour into it they brought my girlfriend in and the look of devastation on her face destroyed me. It was more than I could take."
The case is being investigated by the Independent Police Complaints Commission.
Nottinghamshire Police are conducting an internal review.
Environmental activists in Leeds said their trust had been "abused" when they discovered that a protester they had befriended was in fact an undercover officer.
The policewoman moved to Leeds in 2004 and lived in the city's student quarter before telling friends she had to leave for "personal reasons" in 2008.
It is understood that she was removed from another undercover surveillance operation last week after her identity was revealed on internet messageboards.
Leeds University lecturer Paul Chatterton, who knew the officer, said the operation had further broken the trust between police and the public.