A report from the National Wildlife Federation on the impact of the BP oil spill is not based on science, a spokesman for BP said Wednesday.

The National Wildlife Federation published a report Tuesday that said 14 different species of wildlife were still feeling the effects of the 2010 oil spill in the Gulf of Mexico.

Jason Ryan, a spokesman for BP, said in response to e-mail questions the NWF report was off the mark.

"The National Wildlife Federation report is a piece of political advocacy, not science," he said. "It cherry picks reports to support the organization's agenda, often ignoring caveats in those reports or mischaracterizing their findings."

The U.S. government estimates about 4.9 million barrels of oil spilled when the Deepwater Horizon rig, leased from Transocean by BP, caught fire and sank in the Gulf of Mexico on April 20, 2010. Eleven rig workers died in the incident.

BP said that, as of Dec. 31, it has spent more than $14 billion on clean-up and other activities associated with the spill.

Ryan said a number of investigations were ongoing to determine how wildlife are dealing with the consequences of the spill, though no definitive conclusions have been reached.

Doug Inkley, the lead author of the NWF's report, said bottlenose dolphins in particular are "sick and dying" in areas soiled by the spill.

"The science is telling us that this is not over," he said in a statement.