The NHS has failed to investigate the unexpected deaths of more than 1,000 people since 2011, a leaked report has revealed.
An investigation found a "failure of leadership" at Southern Health NHS Foundation Trust meant the deaths of mental health and learning-disability patients were not properly examined, according to the BBC.
The report, commissioned by NHS England and carried out by auditor Mazars, was ordered in 2013 after disabled teenager Connor Sparrowhawk drowned in a bath at a Southern Health hospital in Oxford. An inquest jury found NHS failings had contributed to the 18-year-old's death.
The leaked draft report, obtained by BBC News, looked at more than 10,000 deaths at the trust between April 2011 and March 2015, of which 1,454 were unexpected.
It found just 195 - 13% - were treated as a serious incident requiring investigation (SIRI) and the likelihood of an unexpected death being investigated depended hugely on the type of patient.
The deaths of adults with mental health problems were the most likely to be investigated, with 30% of cases examined.
But the figure fell to just 1% for patients with learning disabilities and 0.3% among over-65s with mental health problems, the BBC reported.
The report found investigations were of a poor quality and often extremely late, while there were repeated criticisms from coroners about the timeliness and usefulness of reports provided for inquests by Southern Health.
According to the BBC, the report's authors said: "We have little confidence that the trust has fully recognised the need for it to improve its reporting and investigation of deaths."
Connor's mother Sara Ryan said: "This report only confirms that learning-disabled people don't count in life or death. It should not be acceptable in a so-called advanced society."
Deborah Coles, director of the charity Inquest, which has represented Connor's family, said: "This report should send shock waves across the NHS. The failure to investigate deaths of some of society's most vulnerable people is a scandal that must be urgently addressed.
"What is so disturbing is that this report only came about because of the tireless fight for the truth by the family of Connor Sparrowhawk. This damning report must now prompt a national inquiry. Their families deserve nothing less."
A spokesman for Southern Health, which provides services to about 45,000 people across Hampshire, Dorset, Wiltshire, Oxfordshire and Buckinghamshire, said: "There are serious concerns about the draft report's interpretation of the evidence.
"We fully accept that our reporting processes following a patient death have not always been good enough. We have taken considerable measures to strengthen our investigation and learning from deaths including increased monitoring and scrutiny.
"We would stress the draft report contains no evidence of more deaths than expected in the last four years of people with mental health needs or learning disabilities for the size and age of the population we serve."
Despite the leak, NHS England refused to confirm when the final version of the report will be published.
An NHS England spokesman said: "We commissioned an independent report because it was clear that there are significant concerns. We are determined that, for the sake of past, present and future patients and their families, all the issues should be examined and any lessons clearly identified and acted upon.
"The final full independent report will be published as soon as possible, and all the agencies involved stand ready to take appropriate action."