Alberta premier Alison Redford
Credits: IAN KUCERAK/QMI AGENCY
"I find him quite unpredictable with respect to some of his comments," Redford told reporters near Edmonton on Friday.
She also urged him to come clean about whether he sees Canada's resources as a "tremendous benefit" to the country.
"There may be people that don't share that view and he very well may be one of those people," she said.
"But then he has to be clear about that because what it means in terms of his position is that it changes what Canada's economy looks like."
Western leaders have hammered Mulcair for weeks over his 'Dutch disease' comments - an economic theory that the resource boom in Canada is causing some of the manufacturing woes in Ontario and Quebec.
Mulcair is calling for beefed up environment regulations so the cost of pollution is factored into the thriving resource sector - though Redford said Alberta has already found the balance between economic development and environmental sustainability.
Redford and the premiers of British Columbia and Saskatchewan are also miffed by Mulcair's remarks he made this month that they were acting as Prime Minister Stephen Harper's "messengers" with their criticism.
The NDP has denied they aim to play Eastern Canada against Western Canada and said their 'polluter pay' model will benefit future generations.
Muclair will be in Alberta Wednesday and Thursday, and will visit the oilsands north of Fort McMurray on Thursday morning.
Redford was flanked by Natural Resources Minister Joe Oliver, who was in Alberta to talk resource development.
While there, he took the chance to bash the European Union's recent move towards stamping a higher carbon rating on fuel from the oilsands.
He called the EU Fuel Directive "non-scientific" and "discriminatory" and argued the EU rushed into the decision without a full analysis on the impacts of Alberta crude.
"It attempts to pigeonhole, isolate and stigmatize the oilsands based upon an alleged higher emissions level," Oliver said.
The federal government has lobbied hard against the EU decision, over fears it put would Canadian suppliers at a disadvantage.
-- with files from Jackie L. Larson