Scientists and environmental groups are raising questions about 5,000 gallons per day estimate. They also criticize BP for refusing to use scientific techniques that would give a more precise figure.
BP has repeatedly claimed that measuring the plume of oil gushing from the broken well would be impossible.
The issue of how fast the well is leaking has been unclear from the beginning. For several days after the April 21 explosion of the Deepwater Horizon rig, the government and BP claimed that the well on the ocean floor was leaking about 1,000 barrels a day.