The Metropolitan police are to pay more than £400,000 to a woman who has been profoundly traumatised after discovering by chance that the father of her son was an undercover police officer.

It is the first time the police have made a payment to settle any of the legal claims brought by women who were deceived by undercover officers sent to spy on political and activist groups.

The woman has been receiving psychiatric treatment and has contemplated suicide since she read a newspaper in 2012 and found out the true identity of the man who had fathered her son before abandoning her and the child 24 years previously.

The woman, who wishes to remain anonymous and is known by the name Jacqui, said the out-of-court settlement in which the Met would pay her £425,000 would not bring closure for her as the force had not admitted wrongdoing.

She also criticised the police for dragging out the legal action by refusing to concede for two years that the father, Bob Lambert, was one of their undercover officers, even though he himself had already publicly admitted his covert role.

She added there was “absolute proof” that Lambert was the father of their son as there was “six foot of his DNA walking around”. The police’s obstructive attitude had made her last two years a “hundred hundred times worse”.

She said: “It was like they were kicking me all the time. I felt like they had cast me out to the sea, just to leave me, and I was drowning, I was clinging on.” She had previously said she felt as if she had been “raped by the state”.

Jules Carey, Jacqui’s lawyer, called on Sir Bernard Hogan-Howe, the Met commissioner, to give a commitment that undercover police would never use sexual relationships to gather information, a “shameful and abusive practice”.

Jacqui said she hoped to “finally get some answers” from the public inquiry looking into the undercover infiltration of political campaigners set up by the home secretary, Theresa May, following a series of revelations in the Guardian over the last three years.

Police chiefs have maintained that the undercover operatives were not permitted, under any circumstances, to have sexual relationships with the people they were spying on. However, the evidence that has emerged shows that such sexual relationships were routine, and that they often lasted several years.

Police are still resisting legal claims from more than 10 other women who say they have suffered emotional trauma after discovering that their one-time boyfriends were undercover officers.

Jacqui said she was angry that so many questions about her life would remain unanswered because the police were refusing to give her an explanation. “I have had conversations with my psychiatrist about this. It is something that I have to come to terms with. I live in a country that protects its establishment so much that someone like me is nothing to them – I am just like a little ant, and they are like a big elephant stamping on a little ant. I would like all the gaps of the last 30 years of my life filled in.” She had not known anything about Lambert’s undercover role when they met in east London in 1984. He presented himself as Bob Robinson, a long-haired leftwing radical . In reality he was a member of a secret police unit, the special demonstration squad (SDS), and was embarking on a five-year mission to infiltrate environmental and animal rights groups.

Jacqui, then 22, has described how quickly she became smitten by the “very charming and charismatic” Robinson, her first love. Their son was born the following year. She said she was a trusted activist so no one ever questioned him, particularly as they had had a child together.

Jacqui believed their son was his first child. What she was to discover decades later was that Lambert had another family, miles away on the outskirts of London, and already had two young children with his real wife. On the Sunday she gave birth, he had spent the rest of the weekend with his wife and children. “I had a spy who was being paid by the government to spy on me, to the extent that he watched me give birth, so he saw every intimate part of me. He was with me for 14 hours giving birth. How did he report that back?”

She had wanted the child and said he had made no effort to persuade her to have an abortion. At first he was a devoted, hands-on father, but when their son was two Lambert disappeared from their lives and left her to bring him up. At the time he claimed that he had to go on the run abroad to escape from the police who wanted to arrest him over his animal rights work.

In fact, he returned to Scotland Yard and was promoted to detective inspector, running the operations of the SDS in the 1990s. He controlled undercover officers deployed in political groups. Several struck up long-term relationships with campaigners. In October 2011 a group of activists unmasked Lambert, who had left the police and become an academic, compelling him to publish a statement admitting that he had been an undercover officer.

Jacqui did not find out until June 2012 when she read about his undercover work in a newspaper. Within 24 hours she had tracked him down.

She said Lambert and his son had since developed a close relationship.

The Met said it unreservedly apologised for any pain and suffering Jacqui had suffered, recognising “the impact that the revelation that he was an undercover police officer must have had both on her and her son”. It said it had dealt with the case with “professionalism and sensitivity” and regretted if the process had “added to her distress”. Lambert’s confirmation that he was an undercover officer did “nothing to dilute our duty to protect our staff currently working undercover”, the Met said, as it had to preserve the secrecy of covert operations.

Jacqui - in her own words

He watched me give birth. To me, he was watching his first child being born. He was there throughout the labour, and that is something so intimate between a man and a woman, to watch your wife, your girlfriend, your partner give birth to your child is, despite all the blood and gore and everything that’s there, so intimate. And I shared that with a ghost, with someone who vaporised.

As I said, I have no foundations in my life. I had a spy who was being paid by the government to spy on me to the extent that he watched me give birth. So he saw every intimate part of me. He was 14 hours with me, giving birth.

How did he report that back? Did he report every contraction back to the police? What use was that for information purposes? He had to spent all of a Sunday evening right the way through to the Monday at lunchtime[when] I actually gave birth. [He] held our son before I did, because I was out of it.

And after 14 and a half hours and epidural and everything, I was just resting and he was holding our son. Our son was in special care just for a couple of days because of the difficult birth. He came down to tell me how he was, that he had been holding him, and I had not been well enough to go and see him.

He was 36 hours old before I saw him to hold him, but Bob had been with him all that time. He had bonded with him for 36 hours before that. So this spy watched me give birth, the most intimate thing a man and woman can share. And he would have [taken] that secret to his grave, because in all this time he had not told his second wife anything about us.