The minister in charge of Ontario's prisons will not release from solitary confinement an inmate who has spent four years in isolation without trial despite a growing chorus of voices demanding action.

Community Safety Minister David Orazietti is under pressure to let Adam Capay, a 23-year-old First Nations man, out of the Plexiglas-lined cell at the Thunder Bay Jail where he is confined alone under 24-hour-a-day artificial light.

Mr. Capay was charged in 2012 with killing another inmate in a fight, and has not yet come to trial.

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Mr. Capay has become an example of the crisis in the province's corrections system, where a lack of resources has left hundreds of prisoners locked in solitary confinement for weeks, months and years on end.

Globe editorial: Ontario's sickening mistreatment of Adam Capay

Read more: First Nations chief calls prisoner's treatment 'inhumane'

"I cannot commit to releasing any individual from segregation," Mr. Orazietti said at Queen's Park on Tuesday. "That is not a decision that politicians are making. That is a decision that is made by the individuals operating our jails. I will not take individual action on a specific circumstance."

Mr. Capay's situation became public after a prison guard tipped off Renu Mandhane, the head of the province's human rights commission, when she was visiting the jail earlier this month. Ms. Mandhane found Mr. Capay alone at the end of a range on a windowless floor. After 1,500 days in solitary, she later told reporters, he suffered from memory loss and difficulty speaking. Because of the continuous artificial light, he could not tell day from night.

Ms. Mandhane's data showed that, between October and December of last year, 1,383 Ontario prisoners had spent more than 15 days in solitary confinement, a threshold the United Nations calls a form of torture.

Mr. Orazietti refused on Tuesday to order an end to long-term, indefinite solitary confinement in the province's prisons.

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"I can't commit to that right now," he said.

Mr. Orazietti is awaiting the results of a third-party review due next year. He ordered it earlier this month after a previous 19-month review.

He said holding prisoners in segregation for years on end without trial "is not ideal," but is sometimes necessary because of limits on space.

"The physical capacity and limitations of the existing system are such that an individual may, under certain circumstances, be placed in segregation. Is that ideal? It's not ideal," he said. "There needs to be an investment. And there needs to be a review."

NDP community safety critic Jennifer French said the government does not need another review to tell it to cap solitary confinement at 15 days.

"It does beg the question, when you have someone who's been languishing for four years: How many other Adam Capays are there in our jails who have been forgotten?" she said.

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Ms. French said the government needs a plan to fund prison programs properly to help inmates avoid solitary.

"They … have to tackle mental health, they need to be addressing the lack of supports and resources and rehabilitation programs," she said.

Pressure from the public is also ramping up: A change.org petition calling on Mr. Orazietti to take Mr. Capay out of solitary had reached nearly 2,000 signatures on Tuesday.

Hundreds more weighed in on Twitter, including former Ontario premier Bob Rae. "How could this be?" he tweeted above a link to a story on Mr. Capay.

Ombudsman Paul Dubé is also considering launching an investigation.

A correctional officer at the 90-year-old jail said he has been concerned about segregation conditions for at least a year, but that criticism should focus on the criminal justice system, not just prison workers. "Everyone should share the blame," said Mike Lundy, president of the OPSEU local at the jail.

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Mr. Lundy estimates that 35 to 40 per cent of the 140 inmates at Thunder Bay Jail have been diagnosed with a mental-health issue. Yet, unlike some prisons that provide daily psychiatric care, Thunder Bay is visited by a psychiatrist just five times a month for two hours at a time.