Pressed on the subject of the controversial Enbridge Northern Gateway Pipeline project Tuesday, Prime Minister Stephen Harper told reporters the project will be approved on the basis of science, not politics.

The prime minister was at a Vancouver elementary school Tuesday to announce additional employment insurance benefits for parents forced to take time off work to care for a critically ill or injured child.

But after Harper’s morning photo op and announcement, reporters questioned him on the apparent difference of opinion between his government and that of B.C. Liberal Premier Christy Clark on the subject of routing the proposed twin pipelines through her province.

When pressed to reveal what he has discussed with Premier Clark, he was blunt.

"I'm not going to share with you any private conversations with any premier," Harper said, adding: "I'm not going to get into an argument or discussion about how we divide hypothetical revenues."

Clark walked out of a premiers meeting in late July, saying she couldn't endorse their national energy strategy before Ottawa and Alberta agreed on how to compensate B.C. for allowing the $6-billion pipeline to pass through.

Pushed on Tuesday to answer whether he would back a pipeline that snaked through the Northwest Territories rather than B.C., Harper stuck to his message.

"All such projects will go through a thorough independent assessment," he said.

"In a broad sense, without getting into the specifics of any project. . .  we think it's obviously in the vital interests of Canada and in the vital interests of British Columbia," Harper said.

"As Canada's Asia-Pacific gateway, the economic growth we expect to have here in the future is going to be based on commerce with the Asia-Pacific region and we think it's important that we continue to diversify our exports through this province."

Harper's B.C. visit comes amid ongoing debate over the proposed pipeline's future, stoked in recent weeks not only by spills in Enbridge's other pipelines, but also by reports of the company's mishandling of a spill in Michigan two years ago.

His government has a record of enthusiastic support for the project, despite some outspoken, public opposition.

Harper’s own ministers of Foreign Affairs and Immigration were even openly critical of Clark, though his senior minister in B.C., James Moore, said in a Vancouver radio interview last week that Clark was right to expect something in return for the Enbridge routing its pipeline through the province.

Results of a public opinion poll released last week indicated a majority of British Columbians are indeed opposed to the project that would see bitumen from Alberta's oilsands piped to the coastal community of Kitimat for transport to Asia.

In his comments Tuesday, Harper shied away from boosting the project and its potential economic benefits. Instead, he emphasized that the go-ahead is subject to an independent review based on science and not politics.

"The only way governments can handle controversial projects of this manner is to ensure that things are evaluated on an independent basis scientifically, and not simply on political criteria," Harper said.

"That's how we conduct our business," he said. "Projects have to be evaluated on their own merits."

Peter Julian, the New Democrats' natural resources critic, scoffed at Harper’s comments.

"Here's a government that has gutted the environmental assessment process and the (National Energy Board) process, so that politics trump science, trying to tell British Columbians that well, in fact, science will play a bigger role than politics. It's clearly not the case," Julian said.

Recent legislation has set the end of 2013 as the firm deadline for the joint National Energy Board-Canadian Environmental Assessment Agency review panel to complete its work.

Final approval will be subject to cabinet approval, however.

With files from The Canadian Press