Neglect at a care home that had descended into “chaos” amid cost-cutting contributed to the death of Sophie Bennett, a mentally ill 19-year old, an inquest jury has ruled.

The former county-level swimmer, described by her family as “bright, loving and caring”, killed herself at Lancaster Lodge in Richmond, south-west London, in May 2016. Her death followed upheaval instigated by the operating charity, Richmond Psychosocial Foundation International (RPFI), which was advised by the internationally renowned mental health worker Elly Jansen.

Cancelled therapy sessions, the removal of key staff who were then replaced by unqualified people and the introduction of a “boot camp” regime all contributed to Bennett’s death, the jury at West London coroner’s court found.

In the months preceding her death, the charity had changed the home’s resident profile from people with complex mental health needs to those with learning disabilities. The move allowed it to use lower-paid workers. New staff were not qualified in mental health and some agency workers had no experience.

Bennett had complex needs involving bipolar affective disorder, social anxiety disorder and atypical autism, and the jury ruled that cost-cutting possibly contributed to her death. At the end of 2015, the charity commissioned an audit that was presented to Jansen, who was interested in the unit’s ability to maintain itself financially, the inquest heard.

The jury found that Jansen, the charity’s founder, gave advice about the running of the facility without meeting or having any knowledge of the residents. It found the leadership and oversight of the charity’s board was “grossly inadequate”.

Jansen was not on the board that ran the home but owned the building. John Taylor, the coroner, told the jury at West London coroner’s court she was “more or less top of the pyramid of RPFI”.

“The entire structure and stability of Lancaster Lodge was gone,” the coroner said. “There was a general deterioration, psychologically and emotionally … The support structures had broken down ... Lancaster Lodge became like a 1950s asylum: authoritarian, with management control … it became the complete opposite of a therapeutic community, with no safe space.”

He said there were “errors and omissions” in the way the facility was run in the days leading up to Bennett’s death, and steps taken to minimise access to items she could use to harm herself and the observation regime were “grossly inadequate”.

The Care Quality Commission (CQC) found standards to be “good” in 2014 and 2015. But when Wynne Price-Rees, an experienced inspector, was sent to Lancaster Lodge in 2016, he said: “I had never seen anything else like it.”

A new “clinical lead”, Duncan Lawrence, transformed the regime into “a dictatorship – with 19th-century governance”, the inquest heard. Lawrence had a non-medical doctorate, which might have been bought from Knightsbridge University in Denmark, a “degree mill”, the jury were told.

The Care Quality Commission classed the home as inadequate and detailed a lack of person-centred care and insufficiently trained and qualified staff. One staff member, Joanne Chambers, told the jury that by February 2016 the home was “clinically negligent” and “an accident waiting to happen”.

In late April it was proposed that Bennett be moved to another facility, which made her anxious that she had done something wrong. She self-harmed and told staff she had had suicidal thoughts. Advisers on a crisis phone line advised staff that she be taken directly to hospital but she was not.

Bennett was placed on 10-minute watch and her room was searched for items she could use to hurt herself. Only a small blade was found. Some of the staff said they did not think the watch applied when she was in the bathroom, which is where she was found unconscious behind a locked door.

In a statement Bennett’s family – her mother, Nickie, her father, Ben and her three siblings – thanked the jury and said: “We await eagerly to see whether the CQC is to pursue a criminal prosecution, which we believe it should. We also want to see action by the Charity Commission.

“The Charity Commission has been conspicuous by its absence from this inquest despite our urging it to attend and hear the evidence. It has known about the issues surrounding the governance of RPFI since well before Sophie’s death.”

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