OTTAWA — Prime Minister Stephen Harper, a vocal opponent of the long-gun registry who came to power on a promise to scrap it, originally voted in favour of the database as a member of the Reform Party, but switched sides in a final vote.

Sitting on the opposition benches as a Calgary MP, Harper twice voted for Bill C-68 — an expansive package on gun control.

But in a third and final vote in June 1995, he voted with his party by opposing the bill, attributing his change of heart to the will of his constituents.

He said at the time that he had made his initial decision after a poll showed his constituents supported the registry, but then a second poll showed that 60 per cent were against it after learning more about it.

After he switched, he was accused of flip-flopping and rigging the survey to get the result he wanted, according to 15-year-old news stories, while at least one newspaper editorial accused him of retreating from his convictions to toe the party line.

In the 2002 leadership race for the Canadian Alliance leadership, which Harper won, his main rival Stockwell Day took aim at Harper by pointing out his pro-registry votes and suggested he should have voted with the party.

Sara MacIntyre, Harper’s press secretary, said Monday that the prime minister was merely acting as any responsible MP should by casting his vote based on what his constituents wanted.

“That’s consistent with what we’re calling on the opposition to do,” she said. “This is the call — listen to what your constituents are saying to you on the gun registry. In their ridings, they say one thing and they get to Ottawa and see their boss and say something else.”

Harper’s actions of 15 years ago highlight the current government’s “enormous hypocrisy” in attacking opposition MPs who are shifting sides in light of mounting evidence from police that the gun registry helps save lives, said Mark Holland, Liberal public safety critic.

“I think he changed his mind based on ideology. They’re changing mind based on facts in front of them,” said Holland. “It makes it nearly impossible for him to continue his criticisms of people who are looking at the facts and listening to their constituents at third reading when he himself did the same thing on the same issue.”

Third reading is the last stage in the House of Commons before a bill heads to the Senate.

With a vote on whether to eliminate the long-gun registry set for Sept. 22, Conservatives have launched an ad campaign against opponents who plan to withdraw their support for backbencher Candice Hoeppner’s private member’s bill to kill the database.

Her bill passed handily in a preliminary vote-in-principle in the House last November, with the help of eight Liberals and 12 New Democrats.

Liberal Leader Michael Ignatieff is now imposing a “whipped” vote on his rebels to force them to stand with the party in its support for the registry, created by the Chretien government in response to the 1989 Montreal massacre at Ecole Polytechnique.

NDP Leader Jack Layton, while allowing a free vote, is trying to persuade the rural members of his caucus — who sided with Hoeppner — to buy into the NDP “compromise plan” to save the registry.

Next week’s vote is expected to be close, perhaps even a tie.

MPs will cast their votes on a motion, from the Commons public safety committee, on whether to kill Hoeppner’s bill. If the motion passes, the bill dies, but if the motion fails, there will be a further vote on the bill itself.