At least 12 highly vulnerable people with eating disorders have died over the last seven years after failings in care that were so severe that coroners in England and Wales issued legal warnings to hospitals to try to prevent further deaths.

Coroners were so alarmed by the failings that they sent official warnings to 11 trusts that provided care for people with anorexia and bulimia between 2013 and 2019, Guardian analysis shows.

There is a growing crisis in the treatment of eating disorders as doctors struggle to protect young people at a time of soaring demand. Admission numbers have more than doubled from 7,260 in 2010-11 to 16,023 in the year to April 2018.

The cases include:

A 17-year-old girl so underweight when she was admitted to hospital that she was “too ill to survive”.

A 21-year-old woman who had to travel from Kent to London for treatment and took her own life.

A university student who killed herself in front of her parents after being treated in a place where staff had no specialist knowledge of anorexia.

Grace Freeman, a policy and campaigns officer for the mental health charity Mind, said the cases were a “shocking reminder of the poor quality of care too many young people receive from mental health services, particularly those living with eating disorders.”

She added: “When someone is in hospital for their mental health, they are at their most vulnerable and at the very least need to be treated in a safe therapeutic environment, with dignity and compassion. Too often, however, people find themselves receiving care in sub-standard, understaffed facilities.”

A Guardian investigation has established that coroners in England and Wales have served a prevention of future deaths notice in at least 12 cases, identifying problems including a lack of staff or beds.

These notices are issued in the most extreme cases of poor care. The figure of 12 does not cover high failings in care such as in the case of Averil Hart, whose death was described as an “avoidable tragedy”, or Pippa McManus. McManus was severely anorexic and killed herself five days after she was released from hospital.

The 12 cases do include the death of Emma Carpenter, 17, who the coroner said could have survived if she had been admitted to hospital sooner.

Stephanie Haskey, the assistant coroner for Nottinghamshire, concluded in Carpenter’s case: “Death caused by delay in accessing inpatient treatment and no specialist input by paediatricians or physicians.”

She added: “By the time she was admitted as an inpatient … she was too ill to survive and therefore died. While Miss Carpenter was an outpatient, and while she was an inpatient, there was no trust specialist eating disorder service for children and adolescents to which she could have been referred.”

Nottinghamshire Healthcare NHS trust said: “In the time since Emma’s death a number of changes have been made to improve the services available to young people with anorexia. These include more comprehensive liaison with schools and families. In addition, eating disorder services now exist in the city and county, with highly trained, very specialist clinical staff.”

Another woman, Lisa Inkin, 21, travelled from Kent to London for anorexia treatment owing to a lack of support in her area. She took her own life while on home leave.

Her mother, speaking to the BBC in 2014, said there were insufficient hospital beds in Kent for her to be treated in her home county, and she spent a year as a patient in Cygnet Health Care’s Ealing hospital in west London.

She said her daughter told her: “They’ve fixed my body but they haven’t fixed my head.”

Fiona Wilcox, the coroner at Inkin’s inquest, raised concerns about the shortage of specialist beds in Kent and noted that Cygnet had been notified by a friend that Inkin was suicidal but the information was not properly acted upon.

Inspectors have raised concerns about the leadership at Cygnet Health Care, an independent provider of inpatient mental health care, over allegations of abuse at a mental health hospital after a Panorama investigation.

Another anorexia patient, Claire Greaves, 25, took her own life; an inquest jury found care failings contributed to her death in February 2018. Her case was not one of those that led to a prevention notice.

Cygnet Health Care said: “We were deeply saddened by these deaths in 2013 and 2018. Thorough investigations into the specific circumstances were undertaken on both occasions, from which recommendations and lessons learned were implemented.”

Coroners are obliged under the Coroners and Justice Act 2009 to issue a prevention notice if they believe shortcomings by a person, organisation or public body – such as a hospital trust, council or government department – are so serious that other people may die unless urgent action is taken to tackle them.

The issue has come into sharp focus in the east of England as a coroner is investigating potential links after five women died while under the care of Cambridge and Peterborough foundation trust (CPFT). There have been claims their deaths were “completely avoidable”.

The women were Emma Brown, 27, Maria Jakes, who died of multiple organ failure in September 2018, Amanda Bowles, 45, who died in September 2017, Madeline Wallace, 18, who died in March 2018, and Averil Hart, 19, who died in December 2012.

There is no official data on deaths due to eating disorders, and at a recent inquest a doctor said cases were not being properly recorded by the NHS. Suicide is one of the biggest risk factors for people with the condition, with between one-fifth and one-third of patients taking their own lives.

Freeman said: “The government must urgently address workforce issues within the NHS and bring its mental health buildings into the 21st century if we are to avoid more deaths and give young people the care they deserve.”

A Department of Health and Social Care spokesperson said: “Every death from an eating disorder is a tragedy. Attracting and retaining hardworking NHS staff is at the heart of our plans to transform mental health care, backed by an extra £2.3bn extra every year. From September we’re giving all nursing students at least £5,000 a year to fund their living costs.”