Jack Harris, the NDP's justice critic, says Ontario MPs John Rafferty and Bruce Hyer had been warned they would suffer "the consequences" if they broke ranks.
The two went against the NDP's official position and voted with the government this week during the second reading of the bill to abolish the controversial long-gun registry.
Harris said the two members were sanctioned by acting NDP Leader Nycole Turmel — but he did not elaborate on the nature of the punishment.
Dennis Bevington, the NDP member for the Western Arctic in the Northwest Territories, abstained from voting and Nathan Cullen, who is a candidate for the NDP leadership, left the house before the vote.
The fate of the gun registry is a hot-button issue for the NDP.
It is also an acute example of the challenge the party faces as the official Opposition: reconciling the opinions of its members across the country with its new role as the voice of Quebec in Parliament.
The registry was created in the wake of the 1989 massacre of 14 women at Montreal's Ecole polytechnique during a rampage by gunman Marc Lepine, who also killed himself.
Many Quebecers consider the registry a monument in memory of the slain women.
On Wednesday, a group representing the Polytechnique victims urged the Quebec government to sue Ottawa to stop it from destroying the registry data.
Quebec has hinted it might take such action unless the federal government turns over the information to let the province keep its own registry. The feds are refusing to turn over the information.
As for the NDP, Turmel did not indicate Wednesday if the party line would be enforced more rigidly when the abolition comes to its final vote.
Instead, she said there is more work to be done in committee and that the party caucus is unanimous in believing the registry's data should be made available to provinces that want to set up their own registry.
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