A Conservative MP's staff member who wrote a news release calling an organization of Canada's police chiefs a "cult" and suggesting the Liberal caucus beat Michael Ignatieff "black and blue" has resigned, Prime Minister Stephen Harper says.

Conservative MP Garry Breitkreuz, seen in 2002, says he did not write the anti-gun registry news release issued in his name. (Jim Young/Reuters)Liberal Leader Michael Ignatieff led Wednesday's question period with a call for the prime minister to apologize to the Canadian Association of Chiefs of Police on behalf of the government because of a release sent by Saskatchewan MP Garry Breitkreuz's office this week.

The release denounced Ignatieff's decision on Monday to require all Liberal MPs to vote against a private member's bill that would scrap the controversial decade-old registry.

Breitkreuz's release referred to the police chiefs association as "a cult that is led by organizations of police chiefs who pretend the registry helps them do their jobs."

The Liberal leader called on Harper condemn the "disgraceful remarks" in the Commons.

"He accused them of corruption, all because they supported gun registry, which we believe is a vital tool to keep our communities safe and our police officers safe," Ignatieff told the House.

In his reply, Harper informed the House that the MP had already apologized and the unnamed staffer has resigned. He then accused Ignatieff of reversing his position on the "wasteful and ineffective" registry that the government is trying to abolish.

"Mr. Speaker, he's already apologized and we accept that apology," the prime minister said. "What we don't accept, Mr. Speaker, is the leader of the Liberal Party trying to force a policy on members of this House that he himself knows is wrong."

Breitkreuz apologized Tuesday for the "over the top" language in the news release sent under his name, adding he did not write it.

But Liberal MP Dominic Leblanc said it was "cowardly" for Breitkreuz to blame an underling and claim he didn't know the release was being sent by his staff.

"He's not the head of GM with hundreds of people in his office," Leblanc told reporters outside the Commons.

Bloc Québécois Leader Gilles Duceppe said that if the Tories felt someone should resign over the error, then it should be Breitkreuz himself.

"He’s just using one staffer to do what he should do by himself," Duceppe said.

Tory ads target Liberal MPs on gun registry vote

During the last session of Parliament, Conservative MP Candice Hoeppner's bill calling for the scrapping of the registry passed second reading 164-137 in a House vote. It received support from 18 Liberals and New Democrats, most of whom represented northern and rural ridings.

The furor over Breitkreuz's release comes as the Conservatives launched an online advertising campaign targeting Liberal MPs who previously supported the government in November's vote, but were now considering voting with Ignatieff.

On Monday, Ignatieff proposed changes to the registry, including making a first-time failure to register a firearm a non-criminal ticketing offence, while also eliminating fees for new licences, renewals and upgrades.

Breitkreuz's release called Ignatieff's attempt to head off elimination of the registry "an act of desperation that insults the intellect of Canadians."

"His true colours are showing and, if his caucus has any integrity, those colours should be black and blue."

Breitkreuz said he would never use words like cult to describe police chiefs or call on Liberals to beat their leader.

"I don't know how that got out of here," the MP told The Canadian Press on Tuesday.

Despite Breitkreuz's apology, the release was still displaying on his website as of mid-Wednesday.

With files from The Canadian Press