"This is really one huge corporation trying to buy faculty silence in a comprehensive way," said Cary Nelson.

BP is facing lawsuits after the oil spill, which has destroyed the livelihoods of many people along the coast of the Gulf of Mexico.

A copy of a contract offered to scientists by BP, which the BBC said it had obtained, said scientists are not allowed to publish the research they do for the oil giant.

They are also not allowed to speak about the data for at least three years or until the government gives final approval for the companys restoration plan for the whole of the Gulf, said the British broadcaster.

BP said it had hired more than a dozen scientists "with expertise in the resources of the Gulf of Mexico," according to a statement given to the BBC.

Bob Shipp, the head of marine sciences at the University of South Alabama, said BPs lawyers had approached him and wanted his whole department.

"They contacted me and said we would like to have your department interact to develop the best restoration plan possible after this oil spill," he said.

"We laid the ground rules -- that any research we did, we would have to take total control of the data, transparency and the freedom to make those data available to other scientists and subject to peer review.

"They left and we never heard back from them."

Nelson warned BPs actions could be "hugely destructive".

"Our ability to evaluate the disaster and write public policy and make decisions about it as a country can be impacted by the silence of the research scientists who are looking at conditions," he said.

"Its hugely destructive. I mean at some level, this is really BP versus the people of the United States."

BP said it "does not place restrictions on academics speaking about scientific data," according to the BBC.

The environmental disaster began on April 20 when the Deepwater Horizon drilling platform exploded in the Gulf of Mexico, killing 11 workers. The rig sank two days later rupturing the pipe that connected it to the well.