Justin Trudeau is scrambling to explain his stance on gun control, as the Liberal leadership candidate takes flak from opposing sides on the divisive issue.

The presumed Liberal front-runner tried on Monday to mollify both sides of the debate, rekindled over the weekend by his description of the long-gun registry as a failed policy.

Trudeau spent a news scrum with reporters in Saint Jean Sur Richelieu, Que., handling one of the first divisive policy debates to erupt during his campaign.

He explained that he didn't actually flip-flop on the gun registry. Trudeau said he always supported it, and still does support it in principle, but now that it's gone he said it's too divisive to try bringing it back.

In the next breath, however, Trudeau added that he supports Quebec's effort to bring it back in that province because he said the measure is not divisive there.

And he explained why the long-gun registry fits his definition of a "failed" public policy.

"I voted to keep the firearms registry a few months ago and if we had a vote tomorrow I would vote once again to keep the long-gun registry," Trudeau told reporters.

"However, the definition of a failed public policy is the fact that the long-gun registry is no more.… The fact is, because it was so deeply divisive for far too many people, it no longer exists."

He said he would rather spend the next three years, before the federal election, trying to find evidence-based policies that will unite Canadians and not divide them.

The Conservatives had lambasted Trudeau about his remarks, saying that he voted 17 times against abolishing the gun registry.

John Duncan, minister of aboriginal affairs, said, "I thought it was a failure too. If he's agreeing with us. it's a great thing." Asked about why Trudeau would vote for what he termed a failed policy, Duncan answered, "Sounds like a flip-flop, so I don't think that's very consistent, but I don't think Justin Trudeau has been very consistent."

When Trudeau was asked about Quebec's legal fight to keep its portion of the registry, he replied: "I find it's a very good idea. Because in Quebec it was not at all as divisive as it was elsewhere in the country." Trudeau said.

"Perhaps a solution is to let provinces find different solutions. What's important is protecting Quebecers from gun violence."

Blasted by his own party

Meanwhile, Trudeau was being blasted Monday by people inside his party as well. One of his critics included a former Liberal justice minister.

Martin Cauchon, who is still pondering whether to run for the leadership himself, said that leadership contenders need to show they'll stand up for Liberal principles and values.

And he said the controversial registry, created by the government of Jean Chrétien in which Cauchon served, is an important part of the party's legacy.

"I believe that we have to update our policies and make sure that next election we're going to be able to show leadership to Canadians," Cauchon said in an interview. "But, you know what, I believe as well ... that a candidate running should have the backbone to respect and stand for the principles that we have always stood for."

Cauchon said party renewal shouldn't mean Liberals have to turn their backs on accomplishments such as the Charter of Rights, official bilingualism or even the gun registry.

Gun registry a 'key value'

"I do hope that the starting point for our party will be to respect key values and key principles and, to me, the gun registry is an important one ... I can't imagine having one single candidate in our race saying the gun registry — what was the term that he used? — a failure."

Cauchon said the registry was an important part of the Chrétien government's efforts to make the country a safer place. He noted it was supported by police chiefs as a key policing tool.

Prime Minister Stephen Harper's Conservative government killed the registry and destroyed all the data in it — except in Quebec, where the provincial government has gone to court to prevent destruction of the records.

Cauchon acknowledged there were some problems getting the registry off the ground initially, including ballooning costs, although he disputed the $1-billion estimate. But he said it was working well by the time Harper scrapped it.

Cauchon said he believes the registry should be re-created in a manner that will "not compromise the safety of our communities or the security of our people."

He also blasted Trudeau for suggesting last week, in remarks to local Liberals in Hawkesbury, Ont., that gun ownership is an "important facet of Canadian identity" and "part of the culture of Canada."

"The point is pretty simple. We're not living in the [United] States, where Americans have a constitutional right to bear arms. We're building a different society."

Marc Garneau, who is a candidate in the Liberal leadership, said that he wouldn't have characterized the gun registry as a failed policy, as Trudeau did, and that it had its good points and bad points.

Garneau added, "It’s gone now. The Conservatives have killed it. Let’s move on to other things. It is not my intention to spend more money to bring it back."

NDP would revive registry

NDP Leader Thomas Mulcair said that if the NDP forms a government, it would bring back the long-gun registry. But, he said, the pitfalls of the last version of the registry would be avoided by not making making minor infractions a criminal offence.

Two of Mulcair's MPs voted in favour of abolishing the gun registry, and one of them, Bruce Hyer, quit the caucus over the matter and now sits as an Independent.

Asked whether the fact that some of his members might have a problem with reviving the registry, Mulcair said, "The NDP’s position, the position on which I won the leadership, is that we will be in favour of registering arms in this country, period."

With files from CBC News