When Phillip Cranmer killed himself nearly three months ago, his family were at a loss to understand why he had taken his own life. The 20-year-old had no history of mental illness and had been laughing and joking the day before. But it emerged that Phillip had been secretly planning his death for months, logging on to internet chatrooms and surfing the net for tips on committing suicide.

His father, Roy Boffey, has written to the Home Office demanding an urgent investigation into suicide chat rooms. He wants people who run them to face prosecution.

"The website played a significant part [in Phillip's death]," said the retired teacher and hospital chaplain who, lives in Solihull in the West Midlands. "He wasn't suffering in any way. He wasn't having medication or suffering from depression."

There is no official regulation of suicide website chatrooms. Experts believe they are dangerous because they may lead vulnerable young people to encourage one another to end their lives.

Last year 35-year-old Michael Gooden jumped to his death from Beachy Head after entering into a death pact with fellow chatroom user Louis Gillies. Mr Gillies, 36, hanged himself on the day he was set to stand trial for assisting his friend's suicide.

Under existing laws, anyone who helps another person to commit suicide faces a maximum prison term of 14 years. A Home Office spokeswoman said: "If anyone has evidence of a website that is encouraging anyone to commit suicide, we urge them to report this to the police." The Government has already drawn up a national suicide prevention strategy.

However, providing information that enables someone to kill themselves is not necessarily illegal. Charities which support families of suicide victims said more research is needed. "There may be situations where people are encouraged to take their lives," said John Peters, spokesman for Survivors of Bereavement by Suicide. "These sites are not likely to stress the effect that suicide will have on those who are left behind."

The Samaritans said there were benefits in people being able to share suicidal thoughts with others who can empathise with them but said there were "better places" to find such support.

"There was one incident when a guy not interested in suicide was encouraging others," said a spokeswoman. "He was part of a cult who think the world is over-populated.

"It's impossible to know who is using [a chatroom] and if people really are who they say they are. If someone is feeling vulnerable, there are other places that would be more constructive to visit. These sites can be very negative sites to visit."

After Phillip's death, his family learned that he had been logging on to internet suicide sites for more than eight months. His diary entry a couple of days before he died on 8 September read: "The one thing that must not happen is for this to go wrong. I do not want to be saved."

Yet Mr Boffey said there was no indication that Phillip was in emotional distress. Having passed his A-levels, he was looking forward to a gap year before taking a film studies course.Mr Boffey said: "He was perfectly normal nine-tenths of the time, but with the website he had a secret obsession on the subject of death. For reasons we will never know, he chose to take his life.It's not a healthy society that tolerates instructions on how to do this. It's not something to ignore."

Survivors of Bereavement by Suicide: 0870 2413337