Mental health legislation must be overhauled to stop the “horrific” and inappropriate detention of young people with autism or learning disabilities, MPs have said.

The human rights of many young people are being breached in mental health hospitals, causing their lives to be “needlessly blighted” and their families to suffer, a report has found.

Parliament’s joint committee on human rights said it had “lost confidence that the system is doing what it says it is doing and the regulator’s method of checking is not working”.

It is calling for criteria governing detentions under the Mental Health Act to be narrowed to protect people from the “horrific reality” of conditions and treatment.

The Labour MP Harriet Harman, the chairwoman of 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 launched an inquiry in January into the often long-term detention of young people with learning disabilities or autism.

It said it had no confidence in the government’s target to reduce the numbers of people with these conditions in mental health facilities.

In relation to the Care Quality Commission, it said that “a regulator which gets it wrong is worse than no regulator at all”, after it failed to detect potential human rights abuses at Whorlton Hall and other hospitals.

The committee laid out a “predictable” pathway to detention in which a child’s condition worsened, their under-supported family struggled to cope and they were then taken away.

Isolated and without familiarity, their condition deteriorated further, plans to return home were shelved and concerned parents were treated with hostility.

Some parents were excluded from decisions about their child, while others told the inquiry they had been “gagged” from speaking out.

One mother said her son, whose arm was injured after being wrenched behind his back, had to wait 24 hours before being taken to an accident and emergency department.

Another parent told of how their son, kept in seclusion for hours at a time, would bite the wood in the doorframe “out of desperation”.

Some young people were not receiving appropriate medical treatment but were subject to physical and medical restraint, such as psychotropic medication, which was intended for those with a serious mental health illness, the committee said.

The MPs said they believed the biggest barrier to progress was a “lack of political focus and accountability”. They called for a unit to be set up within Downing Street led by cabinet members to drive forward reform.

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.”