People found guilty in some killings should have to serve life in prison with little or no chance of parole, Prime Minister Stephen Harper says.

He made the announcement Wednesday in Scarborough, Ont., accompanied by Justice Minister Peter ​MacKay, that his government is proposing legislation to end parole for those convicted of murders involving:

Sexual assault.

Kidnapping.

Terrorism.

A police or corrections officer.

Particular brutality.

Currently, those who are convicted of first-degree murder face an automatic sentence of life in prison with no chance of parole for 25 years.

Harper said the proposed law would only apply to "a relatively small number of offenders," and a government spokeswoman was unable to provide any examples where the legislation would have applied.

Prime Minister Stephen Harper says Justice Minister Peter MacKay will introduce legislation next week that would keep what Harper calls "Canada's most heinous criminals" behind bars for life with little chance of parole. (Darren Calabrese/Canadian Press)

Harper said those convicted of the crimes listed in the legislation could voluntarily petition the public safety minister for release after serving no less than 35 years.

"Decisions will not rest with an appointed board, but with the federal cabinet," he said.

The bill will be introduced next week, Harper said.

Recidivism rate 3%

Canada's prison watchdog, Howard Sapers, told CBC News in January that 99 per cent of offenders released on day parole last year did not reoffend, and 97 per cent of offenders released on full parole completed their parole without reoffending.

Sapers said it should also be considered that Canada already has "a strong carceral response" to violent crimes. Offenders sentenced to life in Canada spent an average of 22 years in prison prior to conditional release — that's "as much or more time," Sapers said, than offenders in other jurisdictions, including the U.S.

In an interview Wednesday with CBC News, Sapers said it's hard to discuss the bill based on the broad strokes outlined ahead of its tabling.

"We know that life-sentenced offenders actually typically make very good parole risks, for lots of reasons. The level of scrutiny they're under is certainly one of the reasons. But also ... many life-sentenced offenders don't have an entrenched criminal history or criminal lifestyle and they actually make very good release risks," Sapers said.

There have been cases where some life-sentenced offenders have murdered again​," he said, adding that it's difficult to discuss in terms of statistics.

"Nobody wants to see anybody get hurt. And the system has to really put its effort into assessing and managing risk, and that is best done on a very case-specific basis," Sapers said.

Asked whether the government would increase funding for corrections, Harper said that's something the government looks at every year.

"But I would say that this legislation should have minimal cost on the justice system. First of all, we're dealing with a relatively small number of offenders here. Secondly, the costs are over a very long period of time, and in some cases they will be offset by the fact there will actually be fewer parole hearings, not more," he said.

Sapers told CBC News in 2013 that it costs an average of $110,000 a year to house a male inmate. Female inmates cost nearly twice that.

Constitutional limits

Public Safety Minister Steven Blaney said in January that the legislation was coming. Harper has also hinted at it.

Asked last month about the possibility, MacKay suggested there were constitutional limits on what the government could do.

"What I'll tell you is that everything we do, we do through the lens of the [Charter of Rights and Freedoms]," he said.

"We have to be aware that there are constitutional limitations in some cases on criminal legislation, so we have to do it through that lens. And when it comes to denying someone any possibility of parole, this weighs heavy in that — in the balance of that consideration."

The government has had several pieces of legislation challenged through the Federal Court and Supreme Court, and has lost repeatedly.

The House has 11 sitting weeks left before it rises for the summer, leaving little time for new legislation to make its way through debate and committee stages in both the House and the Senate before an expected fall election campaign

Under a law introduced by the Conservatives, the next federal election has to be held by Oct. 19, 2015.

Fanning flames

New Democrat MP Paul Dewar said the NDP wants to review the legislation carefully.

"What we do know is that the government and the Conservatives have brought forward legislation before that hasn't passed the constitutional test, so we want to make sure the attorney general can verify that whatever they're bringing forward is going to actually pass the test of the Constitution, the Charter of Rights [and Freedoms]," Dewar said.

Liberal MP John McKay, who represents the Scarborough-Guildwood riding in Toronto, said Harper went to Scarborough to score political points.

"Those of us who live here frankly do not appreciate Mr. Harper showing up just to fan the flames of fear about crime," McKay said in a news release.

"The prime minister seems to have a paranoid fixation on criminals, even though crime rates have declined, while the rest of us get nothing but government inaction."