ST JEROME, Que. -- On the anniversary of Jack Layton's death, NDP Leader Tom Mulcair promised to run a positive campaign despite attacks from his rivals that he called a sign of desperation.

"We will stay the course with a very positive campaign, and we will talk about what we can accomplish together, and we'll leave the attacks to others," Mulcair said Saturday while attending a campaign event in St. Jerome, northwest of Montreal.

Mulcair had in mind a statement from Quebec Conservative incumbent Denis Lebel, who accused the NDP leader of being "an impostor without principles." The comment was run by a Montreal newspaper which had reported the NDP Leader once denounced the role of unions in elections.

"Such an attack on the part of the Conservatives is a sign of desperation," Mulcair said.

In his statement, Lebel not only accused Mulcair of being "in the same bed as the union leaders he once denounced," but also of changing his tune on recently unearthed positive comments Mulcair once made about former British Prime Minister Margaret Thatcher.

"Thomas or Tom Mulcair -- depending where he is -- is a turncoat who changes his discourse depending on his audience," Lebel said in the statement.

The New Democrat Leader, who was once a Liberal cabinet minister in Quebec, rebuffed suggestions he was an impostor in the NDP, pointing out his long history with the party.

"How can it be opportunist to join a party that had never won a single seat in a general election in Quebec?" said Mulcair.

Mulcair also defended his national child-care strategy, responding to a Liberal critique that the NDP plan would download $3.3 billion in costs to the provinces and territories and disproportionately benefit wealthier Canadians.

"I'm surprised to hear that any other political party would be criticizing 1/8the strategy 3/8 because they've been promising to do just that for the last 30 years -- they just never got it done," Mulcair said.

He added he would work with the provinces and territories and that his plan would not be "one size fits all."

Mulcair was attending a corn roast hosted by local NDP candidate Pierre Dionne, drew a largely partisan crowd. Mulcair, who attended with his wife, two sons and grandchildren, handed out corn and took photos with the crowd at the picnic, which was punctuated by the whistle of an orange miniature train.

Layton, the former NDP Leader who died four years ago on August 22, 2011, loomed large over the event. A moment of silence was held to Layton, who led the "Orange Wave" that resulted in the party's best-ever showing in the 2011 general election. He was widely praised within his party for running a positive, upbeat campaign.