“I’M fighting all the time to try to prove that I’m not lying,” an animal rights activist told the Under­cover Policing Inquiry this week as a Conservative politician became the latest former “spy cop” to fall under the probe’s spotlight.

Jessica – not her real name – told the inquiry how she had, as a 19-year-old vulnerable teenager, entered into a lasting sexual relationship with Andrew Coles, who was in his early 30s at the time.

He had lied about his age as well as his identity, leaving her feeling disgusted and exploited, she alleged in an audio-only hearing on Thursday.

Mr Coles, a former councillor and president of Peterborough Conservative group who has previously denied these allegations, is due to give evidence about his role posing as “Andrew Davey” for the Met’s Special Demonstration Squad (SDS) in the 1990s.

The inquiry is probing decades of work of the SDS – set up to crack down on violent protest movements – which saw detectives have relation­ships and in some cases children with women they had lied about their true identity to.

Their code-names were ripped from the death certificates of children.

Mr Coles is the latest of the former “spy cops” to be summoned to face questions about whether the SDS overstepped the mark.

Jessica told the inquiry that when she started out as a young activist for London Greenpeace and Islington Animal Rights, both based in King’s Cross, she was “vulnerable”, burdened by shame after learning she had been adopted, and grieving the deaths of a series of relatives, notably her brother in a car crash.

On learning Mr Coles was not who he said he was, Jessica recalled: “The worst part was my age. To know that at that age, someone so much older and not who he said he was … it made me feel disgusting. It’s just, it is, it’s disgusting, you know, so much older, you know. I’d had issues, you know, and just the exploitation of me.

“Yeah it’s something I haven’t, something I’m not, I can’t get over. I can’t – I can’t – I can’t come to terms with it properly.”

Jessica spoke about how she had gone on her first “hunt sab” aged 14 before joining the Islington Animal Rights group and London Greenpeace. She recalled at the time how she felt: “Hunting is just appalling and cruel. I wanted to voice my thoughts on it.

“I never enjoyed ‘sabbing’ [sabotaging]. It made me angry that these people wanted to rip some defenceless animal to bits. Once the animal gets away, you know what you’ve done. It’s instant. It made me feel that it was a worthwhile thing to do.”

She said that Mr Coles would routinely show up at a shared house where activists lived together at the time, and that one night he kissed her “com­pletely out of the blue”.

They began regularly having sex, she said, but she was a “pretty awful girlfriend”, adding: “It was not love’s young dream that’s for sure.”

“I was very naïve, I think, and quite stupid, to be perfectly honest,” said Jessica. “Now, I kind of cringe to think of myself back then. It’s not a comfortable thing – someone of that age being interested in someone that’s 19. There’s something wrong about it. It’s bordering on a schoolteacher-student kind of thing.”

Jessica recalled how she felt, around 10 years ago, after discovering he was a “spy cop” in a post on Facebook by a fellow activist Paul Gravett, who lived at the time in Caledonian Road, and had previously given evidence about another secret detective, Bob Lambert’s undercover work in King’s Cross.

She told the inquiry: “I know some people when they hear about them, you know, don’t – take some convincing. But I didn’t. Suddenly there were a lot of things that made sense.

“There’s no feeling sort of like it, you know it’s like huge parts of my life I didn’t have the control and the agency that I thought I did.”

Of Mr Coles’ denial of the allegations of a sexual relationship, she said: “I’ve had to sit here, I’ve had to completely humiliate myself, you know, to try and prove I’m not lying. I’m not lying about it.

“So it’s made it so much more difficult and, you know, the fact of who he is and his position, you know. And the thought that he’s in that same position of power again … I felt it was my responsibility to warn people.”

Mr Coles is the brother of I’m A Celebrity… contestant Richard Coles.

The inquiry continues.