BP has been accused of trying to "buy" top scientists and academics to help its defence against litigation after the Gulf of Mexico oil spill.
BBC yesterday quoted the head of the American Association of Professors, Cary Nelson, as saying: "This is really one huge corporation trying to buy faculty silence in a comprehensive way."
BP, which faces more than 300 lawsuits, says it has hired more than a dozen scientists "with expertise in the resources of the Gulf of Mexico".
The BBC said it had a copy of a contract offered to scientists by BP and that it said the scientists could not publish the research they do for BP or speak about the data for at least three years, or until the Government gives approval to the company's restoration plan for the Gulf.
The BBC said the contract also said scientists could perform research for other agencies as long as it did not conflict with the work for BP.
Bob Shipp, the head of marine sciences at the University of South Alabama, said BP wanted to employ him and his department.
"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," he said.
Nelson was concerned about BP's control over scientific research: "Our ability to evaluate the disaster and write public policy and make decisions about it can be impacted by the silence of the scientists who are looking at conditions," the BBC quotes him as saying.
"It's hugely destructive. I mean at some level, this is really BP versus the people of the United States."
The BBC said BP's statement said that it "does not place restrictions on academics speaking about scientific data".
However, it got New Orleans environmental lawyer Joel Waltzer to look over the contract and he said BP's statement did not match up.
"They're the ones who control the process. They're depriving the public of the data and the transparency that we all deserve," he is quoted as saying.
Some scientists the BBC talked to did not share Nelson's fears.
Irv Mendelssohn, a professor in the Department of Oceanography and Coastal Sciences at Louisiana State University, was among other scientists approached by lawyers acting on behalf of BP.
"What I'm doing wouldn't be any different than if I was consulting with one of the natural resource trustees. I am giving my objective opinion about recovery," he said.
Some scientists approached by BP lawyers have been offered as much as US$250 ($345) an hour.
Mendelssohn said he would negotiate his normal consulting fee, which was between US$150 and US$300 an hour. But he told the BBC that was not why he is doing it.
"Good scientists, they're going to be giving their opinions based on the facts ... What's most important is credibility."