Liberal House Leader David McGuinty speaks to the media during a news conference in Ottawa, Wednesday. ((Adrian Wyld/Canadian Press))

Prime Minister Stephen Harper should put capital punishment to a Commons vote if he really believes it's sometimes appropriate, Liberal House Leader David McGuinty says.

McGuinty was responding Wednesday to comments the prime minister made in an interview with the CBC's Peter Mansbridge. Harper said he had no plans to reopen the debate on capital punishment or abortion, though he personally believes that the death penalty is sometimes "appropriate."

"If Mr. Harper is genuinely in favour of capital punishment ... he should bring a bill to the floor of the House of Commons so he can give credence to his beliefs," McGuinty said. "If his beliefs are being held in check because he's in a minority government, he should explain that."

Harper told Mansbridge he didn't "see the country wanting to" have another debate on capital punishment.

The Liberal Party has been opposed to capital punishment since 1976 and would vote against legislation that would reinstate it, McGuinty said.

NDP MP Joe Comartin also criticized Harper's statements, telling the Globe and Mail capital punishment is "a useless tool in deterring or controlling crime."

Comartin said he expected the PM would "simply make a blanket statement that he or she was opposed to capital punishment," given concerns with wrongful convictions and its effectiveness as a deterrent.