Adults with life-threatening eating disorders face huge waits for vital NHS care and must overcome “appalling failings” to get help, leading psychiatrists have warned.

A report by the Royal College of Psychiatrists highlighted the gap in support available for those over 18, saying that while services for teenagers and children have received an injection of £135m, investment in adult services has failed to keep up.

The report highlights research showing that people can wait up to 41 months for treatment, with adults waiting on average 30% longer than under-18s.

“The parliamentary ombudsman’s report into the tragic death of 19-year-old Averil Hart revealed some appalling failings in mental health services which must be addressed,” said Dr Dasha Nicholls, the chair of the college’s eating disorders faculty.

She said that significant work had been done to try to tackle these issues but it had not yet affected services. She said the NHS long-term plan pledged to improve adult mental health services but it was not yet clear how this would help those with anorexia and bulimia.

“What we now need is for the government to spell out exactly how those improvements are going to be delivered for adults suffering from eating disorders,” she said.

The report comes as data obtained by the Guardian shows there has been a dramatic rise in hospital admissions for potentially life-threatening eating disorders in the last year, prompting concern from experts about a growing crisis of young people experiencing anorexia and bulimia.

Figures show annual rises in hospital visits, with admission numbers more than doubling from 7,260 in 2010-11 to 16,023 in the year to April 2018. The latest figure is up from 13,885 the year before.

Adults must also overcome hurdles before accessing services, such as their body mass index (BMI) being more than 16 or if they are self-harming or misusing alcohol, the report concluded. It said that this could cause major delays to their treatment.

“This situation creates an unacceptable health inequality whereby patients from the same geographical area if they are under age 18 can self-refer to community eating disorder services for children and young people and are seen and treated rapidly.

“In contrast, if they are age 18 or above, they may be faced with multiple gatekeeping hurdles before accessing adult eating disorder services, causing substantial delays to their treatment,” the report said.

Many over-18s were waiting more than three years for treatment, after which time recovery outcomes were poorer as the eating disorder was more established. Those with eating disorders were twice as likely to die prematurely as the general population.

James Downs, who had to wait more than six years for treatment, said: “I first became unwell in my teens but did not get the help I needed as children’s services were not as good as they are now.

“But when I went to adult services I was told I was too unwell for treatment as my BMI was so low and was refused cognitive behavioural therapy. I ended up having to drop out of medical school and tried to take my own life by overdosing.

“Life could have been so much different had I been offered the support I needed when I sought help as an adult.”

Latest NHS data shows 81% of under-18s received treatment within one week of an urgent referral, while 87% of non-urgent referrals were seen within four weeks. These percentages have steadily improved since investment and monitoring began in 2016.

The college’s report calls for parity between child and adult services in terms of access, waiting times and service provision – a recommendation that was made in the parliamentary health ombudsman’s 2017 report into the death of Hart from anorexia.

The scathing report by the NHS ombudsman concluded that Hart had died because of numerous “clear failures of care” by GPs, hospitals and specialists in eating disorders.

Her death in December 2012 at the age of 19 “was an avoidable tragedy” caused by an array of health professionals failing to appreciate how dangerously unwell she was, the ombudsman said.

An NHS England spokesperson said: “The NHS long-term plan – which puts patients’ and clinicians’ opinions at the heart of health service proposals – is committed to improving community-based mental health care for adults, including eating disorder services, and is backed by annual funding increases which will outpace the overall growth in health spending over the next five years – helping an extra 370,00 adults by 2023-4.”

• In the UK and Ireland, Samaritans can be contacted on 116 123 or emailjo@samaritans.org or jo@samaritans.ie. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international suicide helplines can be found atwww.befrienders.org.

• This article was amended on 18 May 2019 to include the word “prematurely” in the following sentence: “Those with eating disorders were twice as likely to die prematurely as the general population.”