The federal review panel for the Enbridge Northern Gateway proposal downplayed the risks of a heavy oil pipeline and tanker terminal at Kitimat, and its endorsement should be rejected, 300 scientists have told Prime Minister Stephen Harper.

The federal cabinet is expected to release its decision on the project this month, after a review panel report in December recommended it is in the public interest.

from two University of B.C. scientists and one from Simon Fraser University, endorsed by academics and graduate students from around the world, was released this week. It says the panel's report took "a broad view of the economic benefits, but an asymmetrically narrow view of the environmental risks and costs."

The benefits come to Alberta oil sands producers from an expected higher price for their crude in Asia. But the environmental risks assessed by the panel are limited to transportation by pipeline and tanker, and omit the risks and emission effects from production and later consumption of the oil, the letter states.

Northern Gateway project leader Janet Holder said the joint review panel (JRP) weighed evidence of from top experts in the field.

"By actively seeking to undermine the work of these experts outside of the JRP process, the signatories of this letter are denying the experts an opportunity to defend their work," Holder said.

The Harper government has signalled in recent weeks it is preparing to green-light the project. On May 14, Natural Resources Minister Greg Rickford and Transport Minister Lisa Raitt for federally regulated pipelines, assigning "absolute liability" for costs and damages of $1 billion even when their operation is not at fault. This is on top of unlimited liability when the operator is at fault or negligent.

On May 27, Rickford announced a new major projects management office for Western Canada, intended to increase aboriginal employment and business opportunities related to pipelines, tankers and safety systems to protect them.

The JRP report cited 209 conditions, including a protection plan for whales and other marine mammals and continued work on heavy oil cleanup.

officials say their marine spill prevention and response capabilities would be more than three times required by existing law. Pipeline steel would be 20% thicker than required, with the pipelines monitored and pump stations staffed around the clock.