A human rights group has accused Shell, Nigeria's biggest petroleum producer, of wrongly reporting on the cause and volume of pollution devastating the Niger Delta and making false claims about clean-up measures.
The future of farmers and fishermen whose livelihoods are destroyed by such spills depends on reports that can be "very subjective, misleading and downright false", according to an independent US industry expert hired by London-based Amnesty International to review documents newly obtained under Nigeria's freedom of information law.
The Amnesty report offers detailed analysis to back long-standing claims that oil companies blame sabotage for spills sometimes caused by corrosion and other faults in ageing pipelines. Sabotage or oil theft means a community is not eligible for compensation.
Shell Nigeria says it "firmly rejects (the) unsubstantiated assertions" and seeks "greater transparency and independent oversight" in reporting oil spills.
"Solutions to the terrible tragedy of oil pollution in the Niger Delta need to be found," said a statement provided in response to the report. Shell was the first company to start producing oil in the delta, in 1958.
Shell repeated assertions that most spills are caused by growing theft that experts estimate at between 100,000 and 200,000 barrels of oil a day.
The report, in collaboration with Nigeria's Centre for Environment, Human Rights and Development, sheds new light on one of the worst environmental disasters in Nigeria, a 2008 spill that affected about 30,000 people in the delta's Bodo creek area and is the subject of a lawsuit in Britain. Some experts say the spill caused the largest loss of mangrove habitat ever caused by an oil spill.
Shell documents say the leak started on October 5 and 1,640 barrels of oil were spilled. Government and community documents say the leak started on August 28.
US-based Accufacts, the industry expert hired by Amnesty, reviewed a video of the leak and estimated that up to 4,320 barrels of oil was flooding Bodo each day for at least 72 days.
When Amnesty challenged Shell with its evidence, the company for the first time said it had turned off supply to the affected pipe and therefore the volume of the spill could not be that high. Yet the video shows oil spurting months later, on November 7.
Shell says it cleaned up the Bodo spill between October 30 2008 and December 2009. But it also says it did not have access to the area to stop a second major spill that began on December 7 2008.
Nigerian regulators have not certified the site as clean, as mandated by law.
Other reports, including by the United Nations Environmental Programme in 2011, have questioned Shell data on clean-ups and remediation.
Amnesty International's report for the first time documented the extent of oil spills in the Niger Delta - at least 3,000 over the past six years by the three main companies producing oil onshore.