The day Tom left his family's terraced house in Leamington Spa for the last time was, his mother later recalled, nothing special. He was midway through his A levels and spending a lot of time on the computer - but that was normal. In fact, Barbara Weed thought that in recent weeks her sometimes fraught relationship with her son had improved. “He seemed more cheerful,” she said. “But I now realise that was because he had decided to leave.”

On returning from work, she found a four-line note on the doormat. Addressed to her and the family, it read: “I need to take an indefinite amount of time away from the family... Please do not contact me.” Although they know where he is, Tom has refused any contact with his mother, father, two brothers and his two half-sisters.

Tom, 18, calls the process he has been through “defooing” - freeing himself from his “family of origin”. The term was coined by the founder of the website under whose “malign” influence Tom's family say he has fallen.

Freedomain Radio (FDR), run from Canada by Stefan Molyneux, describes itself as “the largest and most popular philosophy show on the web”. But Ms Weed has a different description for it. She calls it a cult.

One of the philosophies of Mr Molyneux, himself estranged from his parents, is that adult relationships should be voluntary. Critics such as Ms Weed accuse him of poisoning the minds of vulnerable young people against their families. Ms Weed, a Labour councillor, has appeared on television, radio and in the press to denounce the man she believes is responsible for her son's decision - and for 19 other similar cases.

But in his first interview on the subject, Tom told The Times that he felt liberated by his decision.

“Love should not be imposed upon a child, like a chore on a ticklist: mow the lawn, wash the dishes, love your parents,” he said.

“I started to examine my relationships with people in my family, and came to understand that they weren't for me... I didn't feel like I was listened to by my parents. Whenever I tried to make my preferences felt, they didn't respond in an interested way.”

Since leaving home, Tom has begun a language degree, and lived or travelled with friends during the holidays. Although he sometimes feels guilt - “my mum has a way of pulling the heartstrings, but she is turning herself into a victim” - he says his life has improved. “I am freer to live my life and focus on being happy,” he said. “Do I feel that my mother loves me? That's something that's very hard to answer. I can tell you that I don't love her.”

Although Tom agreed to speak to The Times only on condition that Mr Molyneux was present, he denied that he was being manipulated in any way.

“I've been presented as this naive, passive, manipulable character,” he said. “It's offensive to me. When friends have asked why I am not going home at Christmas, they show curiosity and say ‘fair play'. They are impressed by the maturity, I suppose ... I don't think people appreciate the depth of analysis, objectivity and understanding that we go into on FDR in discussing ideas, thoughts and concepts.”

A previously obscure website, Free-domain Radio has been growing in popularity since it was launched three years ago, to the extent that Mr Molyneux was recently able to quit his job in software and rely on donations. Users pay $50 (£30) a month for “Philosopher King” status and are able to access premium forums. Much of the discussion centres on podcasts given by Mr Molyneux.

It was during one such podcast last April - still available on the internet - that a clearly distressed Tom phoned in asking for advice about his veganism and whether he was right to feel disgust towards people who eat meat. Within minutes the conversation had turned into an analysis of Tom's relationship with his parents.

Mr Molyneux can be heard saying that Tom's feelings towards animals may have come from witnessing someone in authority abusing animals. Last week Mr Molyneux was keen to emphasise that this had been only a thesis. “If Tom had said ‘that didn't happen', I would have said fine and moved on,” he told The Times.

But he didn't. In the podcast, Tom went on to talk about how his father used to shout at and kick the family cat. Mr Molyneux then used Tom's description of his father's anger in general to call his Dad a “f***ing arsehole”, who “gets off on bullying helpless, defenceless children”.

Next it was Tom's mother's turn to be lambasted by Mr Molyneux: “She knew he had sick and disgusting rages before they got engaged, [but nevertheless] married him, and said, ‘I'm going to give him children'.

When The Times suggested to Mr Molyneux last week that he had jumped to conclusions about Tom's family very quickly, he replied: “I know it was very quick... This was my 1,000th podcast of course, so it is some pretty advanced stuff. The question is not the rapidity, but the accuracy.”

Indeed, last week Tom was adamant that his decision to break off from his family was in large part because of his father's behaviour which, although never physically violent, scared him.

“Sometimes he would boil over into this violent rage. He would let it out by swearing, shouting, throwing things. He could trash a room very quickly. It would happen once a fortnight, maybe. My father would be very intimidating, my mother would be very submissive. It was very scary.”

His father, John, denies this. “I'm not a violent person. Trashing rooms? No. Rages? No. I think in any family there's always strife but this is so nonsensical it beggars belief. It is unbelievably hurtful. The whole thing has me questioning everything in my past. It has me doubting myself.

“What I hang on to is that Tom's brothers have been very supportive. They say they have had the same upbringing and haven't noticed this.

“I don't think my son is a liar, I think he is under the most appalling influence from that man, who I absolutely despise. The most important thing I can say is that I love Tom enormously and have great regard for him.”

Tom's reasons for breaking contact with his mother, who is now in the process of divorcing her husband, are less clear - and Tom answers differently at different times. Towards the end of his interview with The Times, he blamed her for “guilting” him into seeing members of the family and pretending to enjoy holidays. “My own sense of being wasn't being appreciated,” he said.

Although Mr Molyneux does not know Tom's family, he goes even further. “Tom's mother did not protect him,” he said, asking Tom to “jump in if I am wrong”.

“She married a man who was violent, had his baby and did not protect him from his rages.”

Ms Weed has heard this argument before. Describing her situation as like a bereavement, she denies the violent rages that Tom described. “My husband shouts a lot. It made me nervous enough to try to manage the children so that he wasn't angry with them. Sometimes things got knocked over, but I don't recall him trashing a room. It just didn't happen ... Oh, and I found the holidays boring too.”

If his mother is implicated by proxy, it is harder to understand why Tom refuses to see his siblings. He will not talk about his sisters, but mentions an occasion when, following a row with his mother, his elder brother texted to say that their childhood was great, and that he should stop being cruel to their mother. “He was making statements contrary to my experience, and also showed no curiosity,” Tom says. “Curiosity” and “introspection” are words that Tom uses a lot.

Mr Molyneux, who spoke to The Times on condition that the entire interview was recorded, says that he has been portrayed as a “brain-tentacled ogre manipulating people through the internet”. But he is not surprised by the reaction to his ideas. “When feminists first began to speak about abuse within marriage, every abusive husband started screaming ‘feminazi',” he said. “If I advised a wife to leave an abusive husband, there would not be articles about how I am a cult leader.”

Ian Haworth, of the Cult Information Centre, has been following Freedomain Radio. He says that one of the first signs of a cult is that it cuts people off from their families.

But in other ways, the definition is less of a good fit. The website is just that - a website - and has no physical existence. Although Mr Molyneux makes money from it, he does not get rich from it, and most of the estimated 50,000 users are not regulars. As Mr Molyneux points out, only 20 of those users have “defooed”.

After the interview, Mr Molyneux e-mailed some of their stories, which included allegations of physical and sexual abuse.

The key claim of Mr Molyneux's critics is that sometimes he is willing to bend the facts to suit his theories - to occasionally dire effect.

Although they discuss their problems over the internet, Ms Weed is one of the few “defooed” parents to speak to the media - many of the others believing that doing so will further alienate their children. She is fatalistic about her chances of being reunited. “Tom wants to be someone who ‘defooed'. I wonder in a way if it's got slightly out of hand and he realises he's exaggerated, but he doesn't want to lose face,” she said.

Last week Tom gave little sign of wanting to rebuild his relationship with his family.

“Before I see them again I want to know what kind of commitments they are willing to give to a relationship with me. I feel I require certain virtues out of a person. I have had 18 years with these people: I didn't like the way I was raised, and they didn't earn my respect. If they haven't been into therapy, haven't had this kind of introspection or been honest with themselves, then what's the point?”

Times recommends

• Ask me about sex, not pay
• Culture clubbing
• Honor Blackman: Words from the wise