Woman questions motives of PC Mark Kennedy's relationships while he spent seven years undercover in the protest community

PC Mark Kennedy's former friends have – understandably – been most reluctant to speak candidly about the aspect of his life that could prove most explosive.

Placed deep undercover for more than seven years in the protest community, where he was known as Mark Stone, the police spy built strong friendships, and left a trail of individuals feeling confused and betrayed.

Tonight, a woman came forward to add to accusations that Kennedy in his undercover role had sexual relationships with women in the protest movement. Her allegations raise important questions for his senior police handlers about his conduct while operating undercover.

Giving details about how Kennedy gained her trust and slept with her many times over the course of a year, Anna, 26, said she felt "violated" by the actions of the police officer.

She now questions whether the British police have allowed a string of undercover agents to use sex as a "tactic" to disrupt and glean information about environmental campaigns.

A foreign national who has been active in the environmental movement throughout Europe, Anna said she met Kennedy in 2005 when she was 21.

"As far as I knew, he was very well connected and very active. He was very keen to help out in any way he could with our campaign. We met in London, and obviously as he was very active in everything I was doing we ended up spending a lot of time together."

She said she developed a sexual relationship with the undercover police officer, and had sex with him more than 20 times during that period.

"This movement is a small clique, so it is not difficult to run into the same people in various different situations. I also met him at various protests, for example in Germany, Spain, Ireland, the Netherlands and Iceland."

She said that she spent time at his house in Nottingham but the relationship eventually "faded out". Now married, she is no longer connected with the protest movement.

Anna, who did not want to give her full name, said there were several other women within the protest movement who Kennedy slept with. "I knew he was seeing other people at the same time and there was never any type of romance involved."

The young mother came forward after reading the Guardian investigation into Kennedy and recognising his picture.

There have been unconfirmed reports that Kennedy, who is believed to have had a wife and children before going undercover, also had a long-term relationship with a woman in Nottingham.

Separately, a German MP, Andrej Hunko, has tabled questions in the national parliament calling for an inquiry into Kennedy, who he alleged "didn't only initiate long-term, meaningful friendships but also sexual relationships, clearly under false pretences".

Kennedy's spying operation, which spanned 22 countries, caused widespread controversy after his role in planning and even paying for the invasion of a power station in Nottingham led to the collapse of the trial on Monday.

The collapse of the trial has been referred to the Independent Police Complaints Commission, but the watchdog has yet to announce an inquiry into Kennedy's seven-year spell undercover.

The Met and the National Public Order Intelligence Unit – the agency that Kennedy was seconded to – have refused to discuss the matter.

Kennedy, 41, has expressed remorse over a controversial operation in which he was required to live among protesters, disrupting, organising and at times even paying for "direct action" protests.

He has apologised to the tight-knit group of people in Nottingham whom he called his friends, saying what he had done was "wrong". He said he hoped it would "never happen again".

It is not clear how much Kennedy's police handlers knew about his activities. However, strict protocol for undercover spies requires them to give detailed feedback about their activities and discuss moral obstacles as they emerge.

"Did the Met know that this was going on, or even encouraged it?" Anna asked. "If he was keeping it a secret from the police then that is different. But I think he had so many friends and relationships with people in the movement that I'm questioning whether this was a tactic – or part of his task – to become more trusted or respected within the scene."

While shocked, Anna said there had always been something that "did not add up" about Kennedy.

She said: "He always had money. He obviously had an income that he never really explained. He told me once that him and his brother made beds out of scaffolding – to sell – and that is how he made so much money. At the time it seemed like a bit of a strange thing to me."

She added: "He was a bit different from all of us. He ate meat, he had a pick-up truck, and just not very hippy in a way. Nevertheless people trusted him, and I think people in this movement are generally accepting and open to people being different.

"In retrospect it is obvious that he was on a mission to make relationships, and make links with people. He talked lots about the people he knew all over Europe."

Did you know Mark Kennedy? paul.lewis@theguardian.com