A helpless disabled woman was "harnessed" into a wheelchair and left alone in a locked room by taxpayer-funded staff meant to care for her, says her mother.

The claims have led to an official investigation into how the 22-year-old severely intellectually handicapped woman was looked after.

She had been dropped off at a respite home in Auckland's Manurewa run by NZCare Group Ltd under contract from the Ministry of Health. The service was designed to give parents of disabled children a break.

The case has thrown a spotlight on the way the ministry supervises care for the intellectually disabled with no "spot checks" of homes.

It comes with a sharp rise in complaints about respite homes to the Ministry of Health - of 12 complaints since 2007, five were made this year.

The woman's mother made the allegations on an internet forum and followed up with a complaint to the ministry. The Herald on Sunday has chosen not to name the woman or her daughter.

She said she dropped her daughter off at the house - then returned after a "strong feeling" things were not well.

"I turned around and drove back to respite [and] found my daughter all harnessed in her wheelchair locked in back flat all by herself. The staff and other clients were in the front house," the woman's mother wrote.

Her daughter has the rare Angelman's Syndrome, a neuro-genetic disorder impairing her mental development. It made her susceptible to seizures and prohibited her from speaking or using sign-language.

The condition was also known for giving sufferers an unusually happy demeanour and enough energy to stay awake for six nights in a row.

She said the respite home was "dismal" and there was "no way" she was taking her daughter back.

One of the mother's friends had visited the home with her. She said her friend's daughter was found "strapped in her chair pointed at the TV ... in a room at back of the house ... on her own ... it was damn near criminal. The look on her face when we turned up nearly broke my heart.

"Any physical development and maintenance is being restricted by her being restrained 24/7 and her emotional enjoyment, growth and stimuli is nil through being secluded completely."

NZCare group manager Donna Mitchell refused to comment on whether staff involved were still working with other disabled people.

She said the company - owned by Healthcare NZ - had met the family to listen to their concerns and launched a full investigation.

"The wellbeing of the people we support is always our top priority. NZCare take all complaints very seriously."

Support group Carers NZ director Laurie Hilsgen said the ministry should be carrying out spot checks on care homes.

"It has always been a concern that these homes can get a significant amount of warning in advance so they can sharpen things up."

She said it meant the ministry might not get a "true picture" of how homes were operated.

"The key issue is that these young people are often non-verbal. They cannot communicate their distress except in their behaviour and are then branded as 'difficult'."

The ministry confirmed it had received the mother's complaint and had ordered a full report from NZCare.

A spokeswoman confirmed there were no "spot audits" for residential disability services.

The ministry had contracts for 30 dedicated respite homes and other "respite beds" around the country.

The Health and Disabilities Commission refused to comment.