Bradford coroner Paul Marks said the death of Gareth Oates, from Stowmarket, Suffolk, could probably have been averted if it had not been for the failings of a number of mental health, social services and education agencies.

Professor Marks said there was a clear gap in provision in psychiatric care for young people between 16 and 18 who were too old for child services but too young for adult interventions.

He warned this was probably a national problem and announced he would be writing to the Secretary of State for Health and the Royal College of Psychiatrists about his concerns.

Gareth Oates died a month after his 18th birthday when he was hit by a train after travelling to Marsden Station, near Huddersfield, West Yorkshire. A three-day inquest in Bradford heard how Gareth was bullied while he studied at West Suffolk College, in Bury St Edmunds, with some students routinely calling him “suicide boy”.

Bradford Coroner Paul Marks heard how his mother, Glenys Oates, mounted a desperate battle to get appropriate mental health intervention for her son in the run up to his death on 2 March 2010. He had already tried to kill himself once and had talked of suicide from the age of 11.

In a narrative verdict, Prof Marks said there were gross failures in the assessment and management of his case meanwhile he was denied access to specialist services “amounting to negligence”.

Charities yesterday said his story underlined the need for better care for those with autism. Mel Carr, transitions co-ordinator at the National Autistic Society (NAS), said: “The tragic case underlines the very real difficulties facing young people with autism as they make the transition into adulthood and the need for support at that time.

“Gareth was let down by a system that failed to recognise his needs. This must not happen again and all agencies must do more to help young people with autism.”