A report published today claims people with learning difficulties face a higher risk of miscarriages of justice.
The Prison Reform Trust claims police safeguards for dealing with suspects with learning difficulties are "patchy and inconsistent".
The report follows the controversy surrounding the case of Jamie Bauld, a Down's Syndrome sufferer who was charged with making a racist assault despite having the mental age of a five-year-old.
It claims police custody officers rely too heavily on the advice of health professionals and there is evidence of poor presentation and follow through of suspects' rights to legal advice.
The report concludes that an increase in support for vulnerable suspects would enhance the justice system by protecting the welfare of the individuals as well as "making prosecution a viable option in some cases which might otherwise be inappropriately discontinued or diverted".
Outgoing chair of the Police Federation, Jan Berry, welcomed the report, saying: "The need to identify and support people with learning disabilities through the criminal justice system, and the process by which some can be diverted more appropriately into healthcare settings, are concerns that have been neglected for too long.
"For many suspects, the first point of contact with the criminal justice system is at the police station. This paper provides a stimulus for further discussion and action not only by the police but also by colleagues in health and social care."
Juliet Lyon, director of the Prison Reform Trust, added: "There is nothing fair about a system where things are not explained or understood and vulnerable people are not represented or protected.
"A single high profile miscarriage of justice catches the headlines but literally thousands of people with learning disabilities and learning difficulties are ill served by a system that is blind to their needs."