A sweeping class-action lawsuit from developmentally disabled people alleging decades of abuse at an Ontario institution could include tens of thousands of people from across the country, the plaintiffs' lawyer said Wednesday.

An Ontario Superior Court judge gave the green light for the $1-billion class action involving former residents of Huronia Regional Centre and their family members.

In an oral decision, Justice Maurice Cullity said he would be certifying the order for the lawsuit against the province of Ontario, and will give his written reasons in several days.

Outside court, former residents of the facility cried tears of relief as they gathered with their lawyer.

"This is a group of people who deserve a chance to tell their story and to get redress for what was done to them," said the plaintiffs' lawyer, Kirk Baert

The allegations have not been proven in court and the province said it will not file a statement of defence until it receives the formal order.

Marie Slark, 56, stood outside the courtroom and quietly described the nine years of abuse she said she experienced while at the institution.

"It was like a herd of cattle, like when they put animals in barns," said Slark, who arrived at the facility at the age of seven.

Slark said she never had privacy, because the bathrooms had no stalls and people showered together in one big room. Slark also said there was emotional abuse.

"If we were caught talking we would have to get up, pull our pants down and walk around in the playroom in front of everybody," she said.

"They put people in straight jackets," Slark said, crying as a friend wrapped her arms around Slark to comfort her.

"They drugged you up," Slark added.

Baert said the lawsuit will go forward for residents who were at Huronia after 1945.

Not only will it include more than 1,000 former residents, Baert said, it could also include tens of thousands of family members.

"Not everyone is still in Ontario, people have moved," said Baert, adding their will be newspaper advertisements, direct mail and news releases to inform people about the lawsuit.

Baert said if the plaintiffs win it would be up to a trial judge to decided how the money would be divided.

The institution opened in 1876 under the name Orillia Asylum for Idiots, and when it closed in March 2009, Huronia was the oldest institution for people with a developmental disability.

Over the years, there were allegations of neglect and abuse made against the institution. There were also several deaths.

In the 1960s, an article described the facility as overcrowded, with beds so close people were lying head to head.

By 1971, a report by Walter B. Williston sponsored by the Ministry of Health, condemned the institution, describing situations where adults were left rocking or aimlessly walking the halls, while others were organized into work gangs. The findings eventually led to another scathing government-sponsored report in 1976, which led to the replacement of the administrator of the facility at the time.

Ontario was once home to 16 institutions. Beginning in 1987, the province moved to close them and place residents in community settings.

In the past, some Huronia advocates argued the centre had become a very different place than it was in the 1960s. They said it was a vibrant community where the residents had dances and parties.