A Nigerian regulator says it wants Royal Dutch Shell PLC's local subsidiary to pay a $5 billion fine for the worst offshore spill in the oil-rich nation in more than a decade.

Peter Idabor, head of the National Oil Spill Detection and Response Agency, said Tuesday he had made the recommendation to Nigerian lawmakers at a parliamentary hearing Monday.

He said the company accepts "equipment failure" caused the Dec. 20 spill at its Bonga deep-water oil field, which it has said saw less than 40,000 barrels of oil pour into the Atlantic Ocean.

Shell spokesman Tony Okonedo said the company did not believe there was "any basis in law for this fine."

He said the company had responded to the spill with "professionalism" and acted with the approval of authorities "to prevent environmental impact."