A federal decision to give conditional approval to Shell to drill in the arctic waters off the coast of Alaska was an egregious error, advocacy groups said.

"Instead of holding Shell accountable and moving the country towards a sustainable future, our federal regulators are catering to an ill-prepared company in a region that does not tolerate cutting corners," Greenpeace Senior Research Specialist Tim Donaghy said in a statement emailed to UPI.

The federal Bureau of Ocean Energy Management conditionally approved Shell's multi-year exploration plan for the Chukchi Sea. Before the company can start drilling, it needs additional permits from state and federal agencies, including those governing the protection of mammalian and endangered species.

BOEM Director Abigail Ross Hopper described the permitting process as a thoughtful one for "potential exploration" in a region that holds significant environmental and ecological worth.

Shell is proposing as many as six wells in a region known as the Burger prospect, located in shallow waters, using the Noble Discoverer and Polar Pioneer rigs.

The Dutch supermajor said in a statement it viewed conditional approval as a sign of regulator confidence in its exploration plans.

"However, before operations can begin this summer, it's imperative that the remainder of our permits be practical and delivered in a timely manner," the company said. "In the meantime, we will continue to test and prepare our contractors, assets and contingency plans against the high bar that stakeholders and regulators expect of an Arctic operator."

Seattle Mayor Ed Murray last week expressed opposition to Shell's lease for a port terminal for use for its drilling plans offshore Alaska. Port officials in January approved plans to lease Terminal 5 to Foss Maritime, which would facilitate Shell's regional operations.

Advocacy groups in the region announced plans for a "sHellNo!' campaign in the state's Elliot Bay to protest Shell's drilling plans. Six Greenpeace activists scaled Polar Pioneer as it moved toward Seattle waters last month.

The company devoted about $5 billion and more than eight years of work for its arctic oil exploration campaign. Its drillship Kulluk struck ground off the Alaskan coast in 2012, and the U.S. Coast Guard blamed harsh winter conditions and the company's efforts to escape Alaskan tax laws for the incident.

Susan Murray, deputy vice president for Pacific operations at advocacy group Oceana, said the arctic campaign is both risky and ill-conceived.

"Accidents can and do happen; and there is no proven way to respond to an oil spill in icy Arctic waters," she said in a statement.

BOEM said it was vetting public comments on standards that specifically address the "challenging and unforgiving" conditions in frigid Alaskan waters.

Shell Chief Executive Ben van Beurden said the company expects a federal review process will be completed in time for the company to start drilling in Alaskan waters at some point this year.