MONTREAL - A Conservative senator is backing away from an unconventional proposal for reducing prison costs: Give convicted murderers a rope and let them decide whether to hang themselves.

"Basically, every killer should have the right to his own rope in his cell. They can decide whether to live," Senator Pierre-Hugues Boisvenu told reporters on Wednesday morning.

Boisvenu later told a Montreal radio station he'd gone too far.

"The comment was altogether inappropriate," he said.

Boisvenu, a victim's rights advocate appointed to the Senate by Prime Minister Stephen Harper, made the original comment to reporters on Parliament Hill. He also said the death penalty should be considered in certain cases when there's no hope of rehabilitation. He said limited use of capital punishment could save money.

Boisvenu cited the case of the Shafias—the Montrealers who were convicted this week of killing four female family members. Boisvenu estimated that it will cost taxpayers $10 million to keep them locked up. They were sentenced to life in prison with no possibility of parole for 25 years.

He also cited the example of serial killer Clifford Olson, who spent three decades behind bars before he died last September.

"In a case as horrible as Olson's, is there really a discussion to be had on this?" he asked. "For people who have no possibility of rehabilitation? People who have killed dozens of women? I don't have much pity for that."

Boisvenu made it clear, however, that he disagrees with regular use of the death penalty. Canada abolished capital punishment in 1976 and the last executions were in 1962.

"The senator has clearly withdrawn those words, I think we all understand that Senator Boisvenu and his family have suffered horribly in the past," said Prime Minister Stephen Harper in the House of Commons on Wednesday afternoon.

The senator's comments follow several high-profile prison suicides in Quebec, in which hanging was the suspected cause.

Interim Liberal leader Bob Rae called Boisvenu's comments "completely unacceptable." Moreover, he pointed out that providing ropes to inmates in hopes of encouraging suicide would actually turn prison officials into criminals.

Rae said Boisvenu can no longer continue to be an official spokesman for the Harper government on its tough-on-crime agenda.

"I don't see how anybody can be a spokesman for the Conservative party in the Senate on justice issues when you've made a statement like that. It's just completely out of line."

Both Rae and interim NDP leader Nycole Turmel said Boisvenu should withdraw from the Senate committee examining the government's omnibus crime bill.

Boisvenu became a prominent victims' rights advocate after his daughter was kidnapped, raped and murdered in 2002. Another daughter was later killed in a car accident. He was appointed to the Senate two years ago.

With files from The Canadian Press.