Washington, Aug 2 (DPA): The US Coast Guard is under fire for allowing huge amounts of chemical dispersants to be used against BP Plc's Gulf of Mexico oil gusher despite strict mandates from the White House to limit their use.

The controversy emerged just days before BP was expected to take the first steps to a permanent closure of the three-month-old rupture still spewing oil into fragile Gulf waters.

The finding of wide use of dispersants was made by an analysis of federal documents prepared by the office of Congressman Edward Markey, the Washington Post reported Sunday.

The dispersants have been deployed to break down the leaking crude oil into smaller particles that are less likely to be swept ashore onto the fragile Gulf Coast, which is the breeding ground for one of the world's most diverse ocean ecologies.

But their use is a "tradeoff" that shifts the ecological burden onto the deep sea life in the Gulf, Carys Mitchelmore, an expert in aquatic toxins at University of Maryland, told CNN. Some organisms deep under the ocean will see the smaller droplets "as food", she said.

Markey found that the US Coast Guard, which is in charge of BP's disaster clean-up, allowed BP to deploy dispersants 74 times over 54 days, both on the surface and deep underwater at the well site.

Thad Allen, the retired Coast Guard commandant who is overseeing things, told the Post that there was a definite decline in the use of dispersants after the May 26 order from the Obama administration to limit their use. Environmental protection officials said their use had declined by 72 percent.