The NDP is putting pressure on Claude Patry, who crossed the floor of the House of Commons to the Bloc Québécois last week, with a robocall to his constituents.

The MP for Jonquière-Alma quit the NDP last week, saying he supported a private member's bill from the Bloc to roll back the Clarity Act, the law that set rules for future referenda on separation from Canada. The bill is up for a vote in the House of Commons Wednesday night.

Clarity Act vote tonight

Patry and other members of the Bloc caucus will vote on their colleague André Bellavance's private member's bill to repeal the Clarity Act Wednesday just after 6 p.m. ET.

It's unclear whether any of Patry's former NDP caucus-mates will join Bloc MPs in voting against the bill, or abstain from the vote entirely.

Several of the NDP's Quebec MPs have admitted to past ties with nationalist groups or pro-sovereignty referendum votes.

NDP Leader Tom Mulcair says that his caucus will not be whipped, but the party's policy suggests New Democrats will vote against the bill.

Patry said he was also opposed to the NDP's position on Newfoundland and Labrador's plan to develop the Muskrat Falls hydro-electric project, which has raised the ire of Quebec.

A copy of the robocall was obtained by Radio-Canada.

In it, the party's deputy national director, Chantal Vallerand, tells constituents in the Quebec riding that Patry was elected to represent them in 2011 as a member of Team Layton. It's a reference to the party's popular former leader Jack Layton, who died of cancer months after the election.

"Last week, he mocked you and all voters in Jonquière-Alma in quitting the NDP to join another political party," Vallerand says in French.

"We believe Mr. Patry should have the courage of his convictions by stepping down and running in a byelection. Since Mr. Patry didn't ask your opinion before making his decision, we decided to do so."

The call then instructs listeners to press 1 to be redirected to a voicemail box where they can leave a message for Patry and provides a toll-free number for the NDP, as well as the address for the party's headquarters in Ottawa.

Mulcair's conduct called 'shameful'

Bloc Leader Daniel Paillé says Patry was attracted by Layton, who wanted to do politics differently.

"Now that we're in the leadership of Tom Mulcair, who falls into the old habits of the Conservatives, and who says we're going to do robocalls, and who says we're going to apply partisan pressure, I think on the part of Mr. Mulcair, it's shameful," Paillé told reporters following question period.

The NDP has long maintained that MPs who cross the floor should resign their seats and run for election under their new party's banner.

Patry has reportedly said he won't step down to force a byelection.

Asked by reporters about the robocall, Mulcair said he had no problem with it.

"I'm extremely okay with that approach by the party. I find that it's outrageous that someone who presented himself with one political party, without having the courage to consult the people in his riding, could quickly change parties," Mulcair said.

2nd MP to cross floor

In January 2012, Quebec MP Lise St-Denis left the NDP to join the Liberal Party. The NDP robocalled St-Denis' constituents but connected them directly to her constituency office if they pressed 1.

Vallerand says Patry made the decision to leave without consulting voters in his riding, so the party was providing an opportunity for them to tell him what they thought about the move.

The call went out yesterday and won't be repeated, she said.

"We're collecting the calls and then we'll find a way of forwarding them to him at some point. So making his job difficult is not the objective here. It's really to make sure that people in Jonquière-Alma know that we're not letting them down."

Vallerand also promised more tactics to come. Mulcair visited the riding over the weekend.

"We're going to be present … There's going to be other means for people to know that we're still present in the riding, but the calls are done."