MONTREAL - The NDP is hoping that a former provincial Liberal cabinet minister can give the party its first electoral breakthrough in Quebec in almost 20 years.

Thomas Mulcair, who was Liberal Premier Jean Charest's environment minister until 2006, will run for the New Democratic Party in Montreal's Outremont riding. No date for the byelection has been set yet.

NDP Leader Jack Layton said Thursday the byelection will be a chance for voters to let Prime Minister Stephen Harper know how they feel about his policies on the environment and Canada's mission in Afghanistan.

"It will send a message to the government of Stephen Harper that the people in this community do not support the direction he's taking on the war in Afghanistan."

Although the NDP says it opposes the war, it maintains it supports the troops.

But Mulcair wouldn't knock Parti Quebecois legislature members who refused to stand Wednesday during a tribute to members of the Royal 22nd Regiment at the national assembly.

The regiment is due to ship out for the war-torn region this summer.

Mulcair, who is also Layton's Quebec lieutenant, said he believes the NDP is on the right track to win Outrement, which has been a Liberal stronghold most recently held by former transport minister Jean Lapierre.

"One of the messages that is being sent to us is that a lot of dissatisfied federalists are taking a good hard look at Stephane Dion and there's a reason why he's at 10 per cent in the polls personally and we're doing better than the Liberals right now."

Mulcair said the NDP, which now has no Quebec seats, is heading into a real race in Outremont, one that be won by "the ones who work the hardest and we intend to be that party."

He represented Chomedey riding in nearby Laval in the Quebec legislature from 1994 until he quit the provincial Liberals earlier this year.

Mulcair, who had been a cabinet minister since 2003, left cabinet in late 2006 because he rejected a switch from his environment portfolio to be minister of government services. He joined the NDP in April.

Phil Edmonston won a seat for the NDP in Quebec in a 1990 byelection, but didn't run in 1993.