Autism Spectrum Australia (Aspect)'s day care centre at Heatherton, Melbourne runs programs for 30 people a day, aged 16 to 50, most of whom cannot talk.
In 2014, staff at the Heatherton Aspect centre built a two-metre-tall wooden box and fitted it with a metal lock.
The box was intended to be used for distressed clients.
The clients were going to be locked inside the box.
Clients had painted the outside of the box.
Egg cartons were going to be fitted inside the box for sound-proofing.
The box was going to be called a "de-sensitising box".
It was intended to be used as a calming device.
Karen Burgess started work at the Heatherton Aspect day care centre in early 2015.
She immediately ordered the dismantling of the box, but says the staff who built it ignored her.
"They laughed and said the box was staying ... they thought it was a good strategy," she said.
"It was just abhorrent," whistleblower Karen Burgess said. "The box epitomises the type of practices that were occuring at that site. There was a complete disregard for the clients as human beings."
A complaint about the box was made to the Victorian Advocacy League for Individuals with Disability (VALID).
They referred the complaint to the Disability Services Commissioner in July 2015.
"Staff were led to believe that it was an approved practice," Aspect employees told the Disability Services Commissioner at a meeting in July 2015.
"Everyone at the site knew about the box."
Aspect sacked Ms Burgess on July 15 2015, listing serious grievances with her performance.
Aspect alleges that Ms Burgess did not work within its policies, she acted outside her authority and she filed paperwork late.
Ms Burgess has brought an unfair dismissal claim against Aspect.
She alleges that she was fired after speaking out about the box.
VALID chief executive Kevin Stone slammed Aspect's treatment of Ms Burgess.
He said she had been put under "enormous pressure, to the point of intimidation".
"It seems beyond belief, and certainly beyond coincidence, that this former senior staff member received a letter of termination on July 15, within hours of the Disability services Commissioner advising the service of its involvement."
In September 2015 Aspect hired a crisis public relations firm.
After hiring the crisis public relations firm, Aspect said it was "impressed"with Ms Burgess's decision to report the box.