Sir Richard Doll made history in the 1950s as the scientist who established beyond doubt that smoking caused lung cancer. He is revered in the medical and scientific establishment not only for what he achieved but the way he achieved it: through painstaking analysis of the evidence. That is why it will be hard for many to believe he could have been influenced by payments from industry that he received but did not declare.

Yesterday his long-time collaborator, the eminent epidemiologist Sir Richard Peto, said such allegations were a deliberate attempt to tarnish the reputation of "far and away the best cancer epidemiologist in the world for a long time" by those who are convinced without sufficient evidence that environmental pollutants, such as toxic chemicals, are a major cause of cancer.

Doll identified the biggest lifestyle cause of cancer - smoking. The research was revolutionary for its time. Cigarettes were considered harmless and 80% of men had a regular habit. Doll and his colleague Sir Austin Bradford Hill embarked on their investigation at the request of the Medical Research Council because lung cancer rates were climbing, but they expected to pin the blame on the fumes from coal fires.

When they administered questionnaires to patients with suspected cancers, they found that all those with confirmed lung cancer were smokers, and all those who got the all-clear were not.

It took some years even after the publication of their paper in the British Medical Journal in 1950 before anybody took any notice. The pair did a second study in doctors, which found high rates of smokers dying from lung cancer. The government accepted the link in 1954. In 1972, Denis Healey became the first chancellor to raise taxes on tobacco, and Doll sent him a congratulatory letter.

Doll went on to establish that smoking also caused other cancers and heart disease. Other work includes suicide and liver disease among doctors, the effects of the contraceptive pill, low-level radiation and gastric ulcers.

Smoking is the biggest cause of cancer and most of the other causes that have been positively identified by Doll and other mainstream epidemiologists are also lifestyle factors - poor diet, for instance, in bowel cancer. Radiation from phone masts and power stations and chemicals in the soil, air and water around us are far harder to pin down and Doll believed there was no proof they played a role, which angered environmentalists.

He took the view that industry was not the enemy: if he worked with them, he would get the data to find out whether or not their chemical output caused cancer, according to Sir Richard Peto, who worked closely with him at the clinical studies unit of Oxford University.

"I think he was pretty open about consulting for Monsanto and other groups," said Sir Richard. "He did certainly believe that it was appropriate to work with industry and try to get them to monitor their workforces."

In the 1950s, says Peto, this approach by Doll and Bradford Hill worked with the asbestos industry. "Initially the asbestos industry called them to try to prove there was no hazard," he said. The regulations on asbestos had been tightened up. "He and Bradford Hill got the data and found there was still a significant hazard."

The company representatives invited the scientists for dinner and tried to persuade them it was not in the national interest to be attacking a major industry, said Peto. Doll and Bradford Hill politely said they would think it over and 24 hours later told the industry they intended to publish. They were threatened with a writ, but went ahead regardless.

Several decades ago, scientists and publishers were not as concerned as they are now over sources of funding. Most of the fees that Doll received, however, went to Green College in Oxford, which he founded and ran as primarily a postgraduate medical institution. When Doll and Peto published their seminal study of cancers caused by workplace hazards in 1981, Doll gave his fee to Green College and Peto requested that his be sent to Amnesty International.

Peto said: "He was very interested in Green College - he gave them hundreds of thousands of pounds over the years. He also gave money to the Medical Foundation for the Victims of Torture."

Consulting at $1,500 a day

Letter sent to Sir Richard Doll by George Roush Jr, director of Monsanto's medicine and environmental health department, on April 29 1986

Dear Sir Richard:

This letter is for the purpose of extending your Consulting Agreement with Monsanto Company dated May 10, 1979. The Consulting Agreement is hereby extended for an additional one-year period beginning June 1, 1986 and ending May 31, 1987.

During the one year period of this extension your consulting fee shall be $1,500.00 per day. All other terms and conditions of the Consulting Agreement of May 10, 1979 shall remain in effect during this extension period.

If the foregoing meets with your understanding and approval please so indicate by executing this letter in duplicate and returning one of the signed duplicates to us.