Federal NDP Leader Thomas Mulcair is standing firm on his view that Canada's oilsands are hurting the country's manufacturing sector, despite backlash from the premiers of western provinces who say his theory is flawed and "divisive."

Mulcair insisted Wednesday that the country's energy exports, particularly from the Alberta oilsands, are artificially inflating the Canadian dollar and contributing to the manufacturing decline across the country -- a phenomenon known as Dutch disease.

In dismissing criticism from the premiers of British Columbia, Alberta and Saskatchewan, Mulcair told The National Post they were simply acting as Prime Minister Stephen Harper's "messengers," provoking more retaliation.

Saskatchewan Premier Brad Wall balked at Mulcair's comments, saying the Opposition leader has his facts wrong.

"What he's doing is very divisive to the country," Wall said Wednesday, noting that new Statistics Canada figures show factory shipments rose by 1.9 per cent in March to $49.7 billion, led by petroleum and coal products.

"Here's someone who wants to be a national leader, who, for the sake of politics, I think, would risk the economic advantage of the country," Wall said.

"I work for the people of Saskatchewan and if Mr. Mulcair is wondering for whom I am a messenger, I am a messenger for the people of Saskatchewan and for the economic interests of this province."

Alberta Premier Alison Redford retorted on Twitter with: "Is this national leadership? @ThomasMulcair continues to make divisive, ill-informed and false comments."

But Mulcair refused to apologize to the premiers.

"My debate is here in the House," he told reporters on Parliament Hill. "My debate is with Stephen Harper."

Mulcair said he has done his own analysis of the oilsands' impact on the Canadian economy, based on Statistics Canada data.

He said more than half of 500,000 lost manufacturing jobs in Canada are casualties of the "artificially high" dollar and the fact that oil and gas companies are not being forced to pay "polluters' fees."

"Those statistics with regard to the overall losses of jobs in Canada are irrefutable," Mulcair said. "And they are directly related to the fact that we're not enforcing federal (environmental) legislation."

Mulcair conceded that changing global trade patterns are responsible for some of those job losses.

Natural Resources Minister Joe Oliver said he was appalled that Mulcair would liken Canada's natural resources to a disease and insisted that there is no negative impact from the oilsands.

In fact, Oliver said, natural resource developments benefit all of Canada, creating jobs and revenue for social programs.

"He's pitting one region against the other," Oliver said of Mulcair.

"It's completely the wrong approach for anybody to be taking," interim Liberal Leader Bob Rae told CTV's Power Play Wednesday, saying Mulcair seems to be "digging himself deeper and deeper" with disparaging comments about a major economic force in Canada.

With a report from CTV's Richard Madan in Ottawa and files from The Canadian Press