A report by the joint select committee on human rights said the practice of detaining children in mental health hospitals is "inflicting terrible suffering on those detained and causing anguish to their distraught families".
The committee said that evidence to its inquiry was so "stark" and consistent that it has "lost confidence that the system is doing what it says it is doing and the regulator's method of checking is not working.
And it warned that too often families of those with learning disabilities and/or autism are "considered to be the problem when they ought to be the solution".
The committee's report highlights the "grim", predictable pathway to inappropriate detention in potentially "brutal" circumstances, with early family concerns raised with the GP or school leading to lengthy waits for assessment and diagnosis while the family struggles on alone, trying to cope.
Eventually some trigger, such as a home move, or a parent falling ill, unsettles the young person and their condition deteriorates. The child is taken away from their home and the familiarity and routine so essential to them, often many miles away and placed with strangers, while desperately concerned parents are treated as hostile and as a problem.
The young person unsurprisingly gets worse and is then put through physical restraint and solitary confinement, which institutions call "seclusion". As the child gets even worse so plans to return home are shelved. The days turn into weeks, then months and in some cases even years.
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Labour MP Harriet Harman, who chairs the committee, said: "This inquiry has shown with stark clarity the urgent change that is needed and we've set out simple proposals for exactly that. They must now be driven forward, urgently.
"It has been left to the media and desperate, anguished parents to expose the brutal reality of our system of detention of people with learning disabilities or autism. We must not look away.
"The horrific reality is of whole lives needlessly blighted, and families in despair. What we saw does not fit our society's image of itself as one which cares for the vulnerable and respects everyone's human rights. It must not be allowed to continue."
The committee made a series of recommendations to address the situation:
- The establishment of a Number 10 Unit, with cabinet-level leadership, to urgently drive forward reform and safeguard the human rights of young people
- Families of those with learning disabilities and/or autism to be recognised as human rights defenders
- The creation of legal duties on clinical commissioning groups and local authorities to ensure the right services are available in the community.
- Narrowing of the Mental Health Act criteria to avoid inappropriate detention
- Substantive reform of the Care Quality Commission's approach and processes including unannounced inspections and the use of covert surveillance methods to better inform inspection judgments.
Earlier this year Children's Commissioner for England Anne Longfield called for reform of the system, warning that many children with learning disabilities and autism are unnecessarily being treated in mental health hospitals.
A Department of Health and Social Care spokeswoman said: "We are committed to ensuring people with a learning disability and autistic people have the best possible quality of life.
"Above all, human rights must be protected and where people do require inpatient care it must be of the highest quality, close to home and for the shortest possible time.
"The number of inpatients with learning disabilities or autism in mental health settings is falling but there is still more to do. The NHS long-term plan will reduce numbers even further by improving specialist services and community crisis care, reducing avoidable admissions and shortening stays in hospital.
"We will consider these recommendations carefully and respond to them in due course."