Prime Minister Stephen Harper took a dig at the NDP Thursday after one of its members crossed the floor to join the Bloc Quebecois.

Claude Patry, MP for Jonquiere-Alma in Quebec's Saguenay region, became the fifth member of the Bloc in the House of Commons, later telling a news conference that he no longer felt at home in the NDP.

"This is an issue that has concerned us for some time, and does concern us: the ambiguity on Canadian unity that we have among some members of the NDP caucus in Quebec," Harper said.

He added that the party has "many, many links" to the sovereigntist Quebec solidaire.

"This phenomenon with 'Bloc orange,' I think, should give everyone some considerable pause, and I think what has happened today is really another example of this particular problem," he said.

During Thursday’s Question Period, Conservative Pierre Poilievre also took an opportunity to dig at the NDP, saying, “Is it the NDP over there or the NDPQ?”

Meanwhile, NDP Leader Tom Mulcair downplayed any suggestion of ambiguity within his party’s caucus and called on Patry to resign and run in a by-election.

“He’s talked about all the people he’s consulted. He just keeps forgetting one thing: he hasn’t consulted his electors on this,” Mulcair said.

Patry had said he joined the New Democrats because, unlike the Liberals and Conservatives, they would understand the needs of Quebec.

Last year, Patry voted in favour of an NDP motion to sit as an independent or run in a by-election rather than join another party.

He's now the third member of the NDP to defect since the election. One joined the Liberals; the other now sits as an independent.

According to political analyst Jean Lapierre, Patry had been complaining privately about his “personal frustration” within the NDP, suggesting he was not getting enough “visibility.”

However, Patry “is not politically dead” because Jonquiere-Alma “is the pickiest riding provincially,” Lapierre told CTV’s Power Play.

Bloc Quebecois leader Daniel Paillé, echoed that notion, saying the important thing was that the Bloc now has a member in the House from another region, and that the party has its roots in Jonquiere-Alma.

The Bloc would need another seven seats to be considered an official party in the House.

With a report from CTV Ottawa’s Daniele Hamamdjian

With files from The Canadian Press