The trust's survey was prompted by the furore last summer when it was revealed that BAT Industries, owner of British American Tobacco, was funding a Medical Research Council unit in Newcastle and a chair at Cambridge University.
"Not only is smoking tobacco harmful to health but there is a belief that the companies will attempt to silence researchers whose findings are unpalatable," said Dr Grant Lewison, from the trust's Unit for Policy Research in Science and Medicine.
He cites the example of a scientist in the US who was told that his research funds would be cut off if he published his results, which showed that inhaling cigarette smoke caused throat cancer in certain animals - a threat that was carried out after publication.
Dr Sandy Macara, chairman of the British Medical Association, said: "It is a sign of how desperate researchers are for funding. But there is no such thing as a free lunch." Annabel FerrimanReuse content