A man whose father abandoned him as a child while working as an undercover police officer is suing the Metropolitan police for compensation.

The man, who has been granted anonymity, alleges in the lawsuit that he has suffered psychiatric damage after discovering at the age of 26 that his father was a police spy, and not the radical protester he had been led to believe.

On Monday in the high court, Mr Justice Nicol ruled against an attempt by the Met to have the lawsuit dismissed.

The ruling clears the way for the man, identified only as TBS, to continue his lawsuit. He has said he wants “to try to get some answers and an apology” from the police about how he came to be born.

TBS said the fact that his birth and childhood were based on a lie had been confusing. “It kind of messes with your identity and who you think you are.”

He told the Guardian he had suffered distress because he had grown up without a father figure. Finding out that this father figure “was denied to me because of the actions of the police is even more distressing because they are supposed to be upholders of the law … But they quite clearly are not,” he said.

The Metropolitan police agreed three years ago to pay his mother, known only as Jacqui, more than £400,000 to settle a lawsuit she had brought.

An undercover officer, Bob Lambert, had begun a relationship with Jacqui during a covert deployment without disclosing to her his real identity.

She only found out by chance that Lambert was a police spy more than two decades after their son, TBS, was born. After the discovery, she contemplated suicide and received psychiatric treatment.

Lambert has been one of the most controversial of the undercover police officers sent to infiltrate political groups since 1968. He was a member of the Met’s undercover unit, the Special Demonstration Squad.

His deployment began in 1984 when he stole the identity of a dead boy and started infiltrating environmental and animal rights groups. He pretended to be Bob Robinson, a leftwing campaigner, and started a relationship with Jacqui, then a 22-year-old animal rights activist.

She has said that when she became pregnant he seemed excited. He was at her side during 14 hours of labour when their son was born in 1985. They lived together for the first two years of his life and, according to Jacqui, Lambert seemed besotted with the baby.

Lambert has been accused of setting fire to a branch of Debenhams in 1987 in a protest against the fur trade – an allegation he denies.

In 1988, Lambert claimed that he had to flee to Spain as the police were on the verge of arresting him for crimes related to his animal rights campaigning.

This was a false story as he had in fact returned to the Met’s headquarters in London and resumed working for Special Branch, later managing the SDS’s covert operations. One of these operations gathered information about the parents of the murdered teenager Stephen Lawrence.

In his real life, Lambert was married with two children. But he concealed his marriage and police work from Jacqui and TBS, and then abandoned her, leaving her to bring up their son as a single parent. TBS grew up believing that his father was a dedicated activist who had gone on the run from the police.

TBS said his family “told me that story – he was really passionate about his animal rights and he had no choice, it was either stick around and get arrested or go, so it was for the best.”

He and Jacqui only found out the truth in 2012 after Lambert was unmasked. She happened to see his photograph in a newspaper article and tracked him down.

TBS said: “It is quite scary to me just how the police can dip in and out of people’s lives. They still seem to struggle with realising the impact of what they have done. They seem to think it’s OK not to talk about it because they have got to protect undercover officers out there.”

He said the police had seemed content to allow him to go on believing the lie that his father had gone on the run. “It just adds to the confusion really – about how I came into existence and who was aware of it, who was making decisions.

“It seems very bizarre that when I was born there was not someone who said: ‘Right, this has gone too far, there’s a whole new life here.’”

In his ruling, Nicol said that it was not justifiable to dismiss TBS’s claim as “it does not seem to me that there is anything factually incoherent in his [assertions]”.

He ruled one aspect of the claim – whether Lambert’s supervisors had committed misconduct after TBS had been born – was not sustainable, and he asked for more submissions from both sides.

TBS’s lawyer, Jules Carey, of Bindmans, said there was “something morally ambiguous” about the police seeking to strike his legal action. He called on the Met to “give [TBS] the answers that he is so desperate for and the apology for their interference in his family life that he deserves”.

The Metropolitan police said: “We note the judgment in this case, which will now potentially continue to trial. It would be inappropriate for us to comment further due to the possibility of future proceedings.”