Canada's Justice Minister says he wants to introduce new legislation to ensure "the absolute worst" offenders are never released, a change that critics warn could lead to increased violence in prisons.

Peter MacKay said the change would be aimed at improving public safety and supporting the victims of violent crime. He made the remarks after the government announced in its Throne Speech this week that it plans to change the laws on life sentences, suggesting for the first time that it would eliminate the possibility of parole for some offenders.

Under current laws, offenders who are sentenced to life in prison for first-degree murder are ineligible to apply for parole until they have served at least 25 years. Asked on Friday if the government plans to eliminate the possibility of parole entirely in some cases, Mr. MacKay said he envisions legislation that would "see a situation where an individual would never be let out of prison, so that they would serve their natural life behind bars."

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Judges already are permitted to extend an offender's parole ineligibility period beyond 25 years for those convicted of multiple murders. But removing even a remote possibility of parole in some cases would be a significant change that legal experts say could be vulnerable to legal challenges.

An online publication titled "A Crime Victim's Guide to the Criminal Justice System" that is available on the website for the federal Department of Justice explains the rationale behind offering offenders a small chance of parole in Canada. "When Parliament abolished capital punishment and introduced mandatory life sentences for murder, it was felt that if rehabilitation was to be successful, persons sentenced to life imprisonment needed some hope of being released during their lifetime," says the guide, which was first published in 2008.

In recent years, the Conservative government has repealed a provision known as the "faint-hope clause" that allowed those convicted of murder a small chance at parole after serving 15 years. The government also passed a law allowing judges to impose consecutive parole ineligibility periods on offenders who are convicted of more than one murder, and abolished the early parole act, which had allowed non-violent offenders to apply for day parole after serving one-sixth of their sentence.

Mr. MacKay said those changes were important to protect public safety and prevent families of victims from being reminded of their loss during an offender's parole hearing. "The primary responsibility of any government, first and foremost, is to protect the public," he said.

The proposed change would apply only to "the absolute worst, violent, multiple offenders," Mr. MacKay said. But some critics worry that eliminating any hope of parole for some offenders could lead to increased violence in federal prisons and against correctional officers by eliminating the most important incentive for good behaviour.

"Although the possibility of successfully applying for parole is remote, it's still a hope. And when you remove a hope... they care less about what happens to them, what happens to their fellow inmates, [and] the risk of violence increases," said Eric Gottardi of the Canadian Bar Association.