Conservative Leader Stephen Harper has accused the NDP of harbouring a "not-so-hidden agenda" to limit the development of Canada's natural resources, after a New Democrat candidate suggested some of Alberta's oil should remain in the ground.

Harper said the NDP wants to "keep the oil in the ground" in Alberta to address the current oil crisis – an accusation that springs from comments made by NDP candidate Linda McQuaig earlier in the week. McQuaig told a television discussion panel on Friday that for Canada to meet its climate change targets, "a lot of the oilsands oil may have to stay in the ground."

Harper called McQuaig a "star" candidate and potential cabinet minister if Thomas Mulcair's NDP come to power, before raising fears over how the New Democrats will treat Canada's natural resources. "The NDP is consistently against the development of our resources and our economy," Harper said at a campaign announcement in Ottawa. "That is the NDP's not-so-hidden agenda on development."

The Toronto Centre NDP candidate's words are contrary to what New Democrat Leader Thomas Mulcair has said in the past. Mulcair has said he is open to exploring oilsands development, including the development of pipeline projects. During the federal election debate on Thursday, Mulcair refused to categorically condemn the Kinder Morgan pipeline project, despite repeated calls to do so from Green Party Leader Elizabeth May.

The NDP has already released a statement distancing itself from McQuaig's comments, which it says are not party policy.

"The NDP believes that developing our natural resources and lowering our greenhouse gas emissions can go hand in hand," a party spokesperson said in an email statement.

Nevertheless, Harper suggested on Sunday that McQuaig's comments were representative of her party's policy, and indicative of what an NDP-run government would be like.

"They have been a disaster wherever they've been in government," Harper said, adding that they would "wreck this economy" if they came into power.

Later in the day, Liberal Leader Justin Trudeau tried to position himself in the middle ground.

"What we see from this exchange is that both of my opponents, Mr. Harper and Mr. Mulcair, are in extreme positions," Trudeau said,  "when what we actually need and what Albertans know, what all Canadians know, is the way to grow a strong economy in the 21st century is by caring for the environment. You don’t get to make a choice between one or the other."