Giving evidence to the parliamentary joint committee on human rights, the father, Jeremy, told MPs and peers that his daughter Bethany, aged 17, has been detained under the Mental Health Act at St Andrews mental health unit in Northampton for the last two years.
For most of that time she has been locked in a cell in isolation where she has been fed through a hatch and allegedly subject to physical abuse, he said.
He read out a statement to the committee from Rebecca Hilsenrath, the chief executive of the Equalities and Human Rights Commission, which is supporting legal action in the case. It criticises the unit, the NHS and Walsall Council, which is Bethany's corporate parent.
"Bethany is living and being treated in shocking and inhumane conditions," said Hilsenrath's statement.
"She has just the same rights as anyone else - she has the right to good-quality health care, she has the right to dignity and she has the right to respect.
"She has, extraordinarily, been kept under lock and key for two years because of repeated failures by Walsall Council, St Andrew's Hospital, Walsall Clinical Commissioning Group and the NHS to arrange support for her.
"She is just a daughter who needs to live near her family, as independently as possible, and this needs to happen now. The Human Rights Act and the Equality Act are there to protect people like Bethany, and it was immensely important to us to help her and her family in this case."
The joint committee on human rights is investigating the treatment of people with autism and learning disabilities in secure assessment and treatment units (ATUs), on the back of an investigation by the Mail on Sunday that highlighted the cases of Bethany and others being detained in units.
Children's commissioner for England Anne Longfield has said she also intends to investigate alleged abuse and maltreatment of children and young people in ATUs.
During his evidence Jeremy explained that Bethany has a form of autism where she struggles to cope with anxious situations and either runs away or is violent.
Conservative peer David Trimble, who was in tears during Jeremy's evidence, asked: "what has it been like for you as a parent?"
"It's been horrific. Being unable to hug your child. Seeing your child on psychotic medication even though she has no diagnosis of psychosis. The fact that you hear that Bethany has been assaulted by staff," said Jeremy.
He also detailed how on one occasion Bethany was allegedly "repeatedly struck" by staff when she tried to put her hand through her door hatch.
Jeremy is also calling for an overhaul of the way young people like Bethany and their families are treated. He said that over two years Bethany's detention in hospital has cost the taxpayer £1.6m.
"What would services like child and adolescent mental health services (CAMHS), GPs, social services be able to do with that amount of money in the way of training and preventing our children going into these units?" he said.
"The money is going into the wrong part of the system. It is not going into prevention."
He also calls for families and patients detained under the Mental Health Act to have a greater say in their treatment and greater investment in community based, therapeutic support services.
Labour MP Harriet Harman, who chairs the committee, said: "We are shining a spotlight on the human rights of individuals who are being shut away and made invisible. Regulation is not enough.
"The only way to stop abuses is to guarantee the full rights of these children, adults and their families.
"We have seen welcome changes towards children on issues such as corporal punishment and learning how to listen to their concerns. Now we need a similar fundamental reassessment of how we are treating people with autism and learning disabilities."
An independent review of the Mental Health Act published this week called for young people detained under the legislation to have more control over their care.
St Andrews Healthcare, which runs the hospital Bethany is detained in, has been contacted for comment. Walsall Council declined to comment.