Prime Minister Stephen Harper is putting distance between himself and Ottawa's conditional approval of a controversial oil sands pipeline, saying from this point on the Northern Gateway project is a matter for arm's-length regulators to work out with proponent Enbridge Inc.

This comes as aboriginal groups in British Columbia join forces to launch a sweeping legal challenge of the federal green light for a project that would pipe Alberta crude to the Pacific and then through coastal waters in supertankers.

The Conservatives appear to be trying to insulate themselves should public opposition to Northern Gateway deepen. A new Angus Reid Global poll suggests Canadians are sharply divided over the plan, with about four out of 10 British Columbians opposed.

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The chief spokesman for Natural Resources Minister Greg Rickford even said it's inaccurate to say that the federal government has approved the pipeline. "It's a 'maybe,'" Chris McCluskey said via his Twitter account.

Mr. Harper went to great lengths Wednesday to emphasize the more than 200 conditions Enbridge must fulfill to proceed with the project. Construction is not expected to begin for at least 16 months.

Hammered in the House of Commons over the decision, the Prime Minister stressed his government was merely complying with an arm's-length review of the project that recommended approval.

"The fact of the matter is … the government is acting on the advice of an independent scientific panel that thoroughly reviewed all matters," he said.

"The government has applied the conditions demanded by that panel and it is now up to the proponent to assure the regulator going forward that it will indeed comply with those conditions."

NDP Leader Tom Mulcair asked why Canada should trust Calgary-based Enbridge after a 2010 spill in Michigan, recalling a U.S. regulator later called the pipeline company, "the Keystone Kops" over its handling of that accident.

Finance Minister Joe Oliver rejected the notion the government is distancing itself from what may prove a controversial decision. "We're not creating any distance," Mr. Oliver said. "In this case, the regulator said this is good for the country, there isn't an environmental problem. So we said yes."

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The NDP is hoping the 2015 federal election in B.C. will end up being a referendum on the pipeline.

In a taste of what's to come, protesters occupied the constituency offices of James Moore, the Harper cabinet's minister for B.C., on Wednesday.

An Angus Reid Global online poll taken after Tuesday's announcement found 37 per cent of respondents think the decision was right, while 34 per cent say it was wrong and nearly one-third are unsure. The poll, which Angus Reid Global paid for, also found 25 per cent of British Columbian respondents believe the conditions "don't even begin to address" their concerns.

Conservative MPs from B.C. offered mixed reactions to the Northern Gateway decision Wednesday, with some defending it, others avoiding reporters and another cautioning the pipeline may not get built.

Emerging from a caucus meeting in Ottawa, some avoided the issue. Minister of State for Seniors Alice Wong remained silent and jogged down a staircase, away from reporters, when asked about the pipeline. Dan Albas, a parliamentary secretary to Treasury Board President Tony Clement, said he could not comment on the project because he had to attend a French lesson.

David Wilks, the MP for Kootenay-Columbia, defended the project and said opponents are fear-mongering in a bid to block it.

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"Not once in British Columbia in 50 years has that happened," he said of the potential for an oil spill.

MP Mark Warawa, who represents the riding of Langley, acknowledged his constituents are split on the issue, and that he shared those concerns with Mr. Rickford.

Peter Lantin, the president of the Haida Nation said B.C. First Nations are uniting to launch a sweeping legal challenge against the federal government over its approval of the Northern Gateway pipeline.

The legal challenge would involve dozens of individual bands as well as all three major aboriginal organizations in the province: the pro-treaty First Nations Summit, the anti-treaty Union of B.C. Indian Chiefs and the regional branch of the Assembly of First Nations.

With reports from Bill Curry and The Canadian Press