Prime Minister Stephen Harper is rejecting a last-ditch appeal from the Opposition Liberals for a compromise on the federal long-gun registry ahead of a key vote on its fate.

Prime Minister Stephen Harper says his government will continue to work so that the federal long-gun registry is abolished. (Adrian Wyld/Canadian Press)

Liberal Leader Michael Ignatieff and NDP Leader Jack Layton have confirmed their entire caucuses will be at Wednesday night's vote to scrap a Conservative backbencher's bill to repeal the 15-year-old registry brought in by the Liberal government of Jean Chrétien.

During Wednesday's question period, Harper said the "vast majority" of gun owners in this country support "responsible" gun control.

"What they do not support is a registry that is costly, ineffective and targeted against them, instead of against real criminals, and we’re going to keep fighting until we get it abolished," the prime minister told the House.

Ignatieff urged Harper to work with opposition parties to maintain the registry, saying it helps protect women against domestic violence.

"The police want this registry, so do doctors," Ignatieff told the House. "Why does the government persist in exploiting division over this issue rather than bringing Canadians together?"

But the prime minister replied that the registry "does no such thing," and called on the Liberals to support the government's other measures to target criminals, instead of targeting their efforts against law-abiding citizens.

The highly anticipated vote on the House public safety committee's motion to defeat Tory MP Candice Hoeppner's private member's bill is slated for around 6 p.m. ET and follows weeks of high-pressure negotiations, cajoling and arm-twisting.

A matter of hours

Layton, speaking to reporters Wednesday after his party's caucus meeting on Parliament Hill, said his party was "very confident" the gun registry will survive the vote, but would not offer any clues on whether all his members would vote in favour of the motion.

"Each of our members have their own approach explaining what they'll do and we'll know this when the vote happens just a few hours from now," he said.

The Liberals — under orders from Ignatieff — and the Bloc Québécois are poised to vote to halt Bill C-391. The Conservatives are set to support the bill, meaning the fate of the registry lies with the NDP, which allows its MPs to vote however they want on a private member's bill.

Six of the dozen New Democrat MPs who initially voted to repeal the registry have now said they will vote to keep it. Only New Democrat MPs Niki Ashton and Nathan Cullen haven't indicated how they will vote.

Earlier in the day, Ignatieff confirmed all his MPs will show up.

"Yes, a straight answer to a straight question," Ignatieff told reporters in the House of Commons foyer.

Simms to switch vote

But Ignatieff, who was flanked by most of his Newfoundland and Labrador caucus to show solidarity with the province as it recovered from the effects of Hurricane Igor, did not say whether all his MPs would vote in favour of the motion.

CBC News has learned Scott Simms, a Newfoundland Liberal MP who previously supported Hoeppner's bill and was notably absent from Ignatieff's scrum, had earlier informed caucus colleagues he was switching his vote in order to preserve the registry because his 79-year-old father had used a firearm to commit suicide.

After media reports emerged of his emotional address to caucus, Simms told the CBC's Rosemary Barton he would not be giving interviews.

Labrador MP Todd Russell, one of the eight Liberal MPs who initially supported Hoeppner's bill last November, would not answer reporters' questions on the vote.

If Hoeppner's bill is defeated, Ignatieff said his party will work to maintain the registry while also pushing for a compromise that would "heal any divides" between rural and urban Canadians on the issue.

The Liberals and NDP have proposed similar changes to the long-gun registry, such as making a first-time failure to register a firearm a non-criminal ticketing offence and waiving fees for new licences, renewals and upgrades.

But the Conservatives have ridiculed the opposition parties' proposals, saying they would remove the federal government's jurisdiction over the registry, while failing to reduce the cost of a "wasteful" program that they argue does nothing to prevent violence.

Flaherty speech 'amusing'

NDP Leader Jack Layton says all his members will be in the House of Commons for Wednesday's crucial vote on the fate of Tory backbencher Candice Hoeppner's bill to repeal the federal long-gun registry. (Sean Kilpatrick/Canadian Press)Ignatieff also hit out at Finance Minister Jim Flaherty's campaign-style speech on Tuesday that raised the spectre of a tax-hiking Liberal-NDP-Bloc coalition and compared the Liberal leader with a pirate trying to seize the helm of Canada's economy at a time when its recovery remains fragile.

Ignatieff said the speech shows that Harper's Conservatives try to govern through fear.

"They first tried to make Canadians afraid of the census," he said. "They've tried to make us afraid of Russian planes up in the Arctic and now, amazing, they're trying to make Canadians afraid of an election, they're trying to make Canadians afraid of democracy.

"It's one of the most amusing things that's happened all week."

Hoeppner hits out at 'bizarre' NDP behaviour

With the backing of enough New Democrat MPs, it appears the Liberal motion to scrap Hoeppner's bill will pass 153-151.

The Manitoba Tory came out swinging against the opposition parties on Wednesday, calling the behaviour of NDP MPs on the issue "bizarre" and saying the Liberals are content to criminalize "law-abiding citizens" who own guns.

She said it was no longer worth trying to convince certain opposition members to change their minds and back her bill.

"They want to put hunters and farmers in prison; we don't want to agree with that," she said surrounded by her Conservative colleagues following their caucus meeting on Parliament Hill.

With files from The Canadian Press