Liberal Leader Michael Ignatieff says NDP Leader Jack Layton and his deputy Thomas Mulcair can side with the police or Prime Minister Stephen Harper on the fate of the federal long-gun registry.

Liberal Leader Michael Ignatieff walks along the shores of the Bras d'Or Lake on Tuesday in Baddeck, N.S. (Mike Dembeck/Canadian Press)"Make up your mind, Jack. The hour is getting late," Ignatieff said during an address to the Liberal caucus on the first day of the party's summer retreat in Baddeck, N.S.

Layton has indicated he will give his MPs a free vote on Conservative backbencher Candice Hoeppner's private member's bill to repeal the registry.

The challenge comes after MPs on a parliamentary committee studying the issue received an RCMP report on the Canadian Firearms Program that called the registry a "critical component" of the program and an important tool for law enforcement.

During the last session of Parliament, Hoeppner's bill, C-391, passed second reading 164-137 in a House vote with support from 12 New Democrats and eight Liberals, most of whom represented northern and rural ridings.

But since then, Ignatieff has declared future votes on the bill whipped, meaning Liberal MPs must vote with their party or face discipline.

In April, he also proposed changes to the registry that he said would remove the "frustrating" elements of the registry to address "legitimate criticisms" from rural Canadians.

Several Liberal MPs who voted in favour of Hoeppner's bill have indicated they will switch their vote when it is put to a third vote in the upcoming session. A vote on a motion passed by the House public safety committee to scrap Hoeppner's bill is scheduled for Sept. 22.

Comartin 'hopeful' MPs will defeat bill

On Monday, Layton said his party would immediately introduce legislation when the fall parliamentary session resumes to make a first-time failure to register a firearm a non-criminal ticketing offence and to waive fees for new licences.

Layton also accused the Conservatives of using the registry as a wedge issue to divide Canadians and hit out at Ignatieff for only proposing changes to the registry once his party forms a government.

But Liberal public safety critic Mark Holland said there's no way such a bill could pass before the final vote on Hoeppner's bill.

"You can't improve something that's gone," Holland told CBC News.

Speaking on Tuesday in a panel interview on Power & Politics with Evan Solomon, NDP Justice critic Joe Comartin said he was "hopeful" that enough of his colleagues from rural and northern ridings would vote against Hoeppner's bill if the NDP's proposed legislation failed to pass in time.

"At this point … we're very close to having enough of them say to C-391: 'This is not the way to go,' [to] say to the country, 'There's a way of reaching a compromise here that will be acceptable to the vast majority of Canadians'," Comartin said.

"So, I expect that, in fact, we, ultimately, are going to defeat C-391 — unless we can reach the compromise before we reach that stage."

Mulcair said it was up to the Liberals to get on board with the NDP's plan if they are serious about the registry.

"If the Liberals want to improve the registry, which they say they want to do, then they can vote with the NDP law that we're going to be presenting," he said.

The Liberal women's caucus announced it is planning a cross-country tour to defend the long-gun registry, which was brought in by the government of Jean Chrétien in 1995 in response to the killing of 14 women at Montreal's L'École Polytéchnique in 1989.

With Ignatieff's challenge, the Liberals appear to be directly targeting Mulcair, who wrested the prized Montreal riding of Outremont from them in a byelection in 2007.

Surviving victims and relatives of those killed in the L'École Polytéchnique massacre, as well as more recent fatal shootings at Dawson College and Concordia University, have publicly called on Mulcair and his caucus colleagues to save the registry by opposing Hoeppner's bill.

The Conservatives have denounced the long-gun registry as wasteful and ineffective, arguing it criminalizes law-abiding Canadians who fail to register a firearm.

Party will fight for 'hard-pressed' middle class

Ignatieff's speech differed from his aggressive address at last summer's caucus retreat, in which he declared Harper's "time is up" — only to back down from defeating the Conservative government in subsequent sessions.

During his address Tuesday, the Liberal leader said "truth and transparency" will be the hallmark of his party's platform.

Ignatieff again painted the Liberals as Canada's "big red tent" in the political centre, insisting his party would fight for "hard-pressed, middle-class Canadians" and "champion" issues like early-learning education, universal health care and pension security.

He said the prime minister has been going around the country saying "everything is terrific," then worked in a barb against the government's plan to scrap the mandatory long-form census.

"You begin to ask yourself, how does he know?" Ignatieff said. "He doesn't care about statistics, that's for sure."

Ignatieff also urged his caucus to sustain the momentum from the summer bus tour into the fall session, but also issued a warning about their Conservative opponents.

"We're up against the toughest and most ruthless machine in Canadian politics," he said. "Never forget that for a second."