Hundreds of thousands of the most vulnerable people in society are being denied the support they need during police interviews, it has been revealed.
Up to 280,000 people with learning disabilities, mental illness or autistic spectrum disorders are interviewed every year but only about 45,000 of these involve the use of a Appropriate Adult (AA) who supports them through the process to ensure they are safe, well, and understand everything that happens.
Home Secretary Theresa May said this lack of AAs, who were introduced to prevent miscarriages of justice, was unacceptable - but an eminent voice in policing and mental health pointed out how it is "extremely difficult, even impossible" for officers to ensure AAs are provided.
Inspector Michael Brown, mental health co-ordinator at the College of Policing, said officers and staff are forbidden from performing the role and other agencies, such as social services, have no duty to provide an AA.
The findings are in a report, commissioned by Mrs May, which calls for a legal duty to be placed on police and others to ensure mentally vulnerable people are interviewed with AAs present. The same duty already exists in relation to children.
One senior stakeholder said AA provision was "a gaping hole. No one owns it, no one scrutinises it, and nobody inspects it. It needs to change."
The report surveyed police custody sergeants who said they particularly struggled to get appropriate adults during weekends, evenings and overnight.
Some reported spending hours trying to find a suitable AA, admitting to sometimes asking random members of the public or proceeding without one.
Of those who completed the survey, around a third said they received no training in identifying vulnerable suspects.
The report describes a teenage boy who was arrested at his family home. His mother told police he had a brain disorder which meant he struggled to concentrate and often spoke before thinking.
She was told he did not need an AA and that she could not support him in the police station, leaving her upset and angry.
Mrs May said: "Appropriate adults provide vital support and help to de-mystify what can be a confusing, sometimes frightening, experience in police custody."
She added: "The status quo is not acceptable and I am concerned that vulnerable adults are not always receiving the support of an appropriate adult.
"We are currently examining the recommendations and implementation options to ensure that vulnerable people are provided with the support they are entitled to."
Chris Bath, chief executive of the National Appropriate Adult Network, the charity which led the study, said: "People with learning disabilities, mental ill health, traumatic brain injuries or autistic spectrum disorders are some of the most vulnerable citizens, and state detention is perhaps the most vulnerable situation.
"We have a moral and a legal duty to ensure appropriate adults are available wherever people live."