OTTAWA -- Interim Liberal leader Bob Rae is calling for a public inquiry to get to the root of the tragedy that befell Ashley Smith, the troubled teen who choked to death in her prison cell as guards stood watch.

And he wants the inquiry to go beyond the particulars of Smith's death to expose the general inability of the prison system to cope with mentally ill offenders.

Rae made the call Thursday after concluding the government of Prime Minister Stephen Harper won't on its own reveal everything it knows about the Smith case.

He expressed frustration that the Conservative government has not responded to his repeated questions as to whether more videos exist documenting the mistreatment of Smith and other mentally ill offenders.

Since the release last week of two disturbing videos showing Smith being restrained with duct tape and injected with powerful anti-psychotic drugs against her will, the government has said it's ordered corrections officials to co-operate fully with a coroner's inquest into Smith's death.

That's sufficient to ensure the inquest will get to the bottom of the tragedy, Public Safety Minister Vic Toews suggested Thursday.

"This matter is being dealt with in a public forum and in a fully transparent way," he told the House of Commons.

But Rae said that's not enough, since the inquest is only empowered to look into the last 12 months of Smith's five years in custody.

"The government must have other videos of Ashley Smith in its possession. It's inconceivable that it would only have two and none others. It must have some that relate to all her period in prison," Rae said later outside the Commons.

"And secondly, it defies logic to think that they only have two videos of one patient or one client of the system."

Based on calls and letters received by Liberals, Rae said there are evidently numerous other cases in which mentally ill offenders have been mistreated.

"And I'm saying if (corrections officials) kept video evidence with respect to how they treated Ashley Smith, they must be sitting on a ton of other evidence."

NDP public safety critic Randall Garrison pointed out that correctional investigator Howard Sapers and his staff reviewed more than 60 hours of video tapes regarding Smith's treatment while in custody before making recommendations two years ago aimed at preventing another similar tragedy.

Among other things, Sapers recommended that the correctional service update and publicize a mental health strategy, allocate resources to fully fund it and implement it by the end of 2012.

Garrison urged Toews to commit to implementing those recommendations immediately. Toews did not directly respond.

He reiterated the government's line that the mentally ill do not belong in prison and that it has taken "concrete steps" since 2006 -- including an investment of $90 million -- to improve access to mental health treatment and train corrections staff.

In a recent interview with CTV's Question Period, Sapers said there were 160 "use of force" incidents involving Smith during the 11-and-a-half months she spent in federal custody. Following her death, he said he examined nine other in-custody deaths and found "some very similar circumstances and patterns of behaviour."

Smith, was first arrested at 13 for assault and causing a disturbance. She got into more trouble for making harassing phone calls and pulling a fire alarm and was finally thrown in jail at age 15 for throwing crab apples at a postal worker.

She was bounced around to various prisons across the country. Much of her final year of life was spent in segregation due to numerous instances of self-harm and choking herself.

Smith died at age 19 at a prison in Kitchener, Ont., after wrapping a strip of cloth around her neck and strangling herself. Guards who were standing watch outside her cell did not step in. They've said they were instructed not to intervene unless Smith stopped breathing.