The entire system of private medical and life insurance is likely to be forced to shut down by the middle of the century because of advances in genetics, one of the most influential voices in British cancer research has told the Guardian.

Sir Paul Nurse, the Nobel prize-winning scientist who jointly heads the charity Cancer Research UK, said private insurers would not be able to deal with the predictive power of genetics and that an expanded version of the NHS was the only way forward.

"I think the insurance system, for individuals will simply go defunct," he said. "I think we should look much more to society taking responsibility for its individuals. Thirty to 50 years from now, you have to have social medicine and society-based insurance systems."

In an interview for a Guardian series on the state of cancer treatment in Britain, which starts today, Sir Paul said that despite the ethical barriers, he believed society and the government would one day embrace large-scale screening for susceptibility to diseases such as cancer.

This would involve cataloguing sets of genetic mutations found in all individuals. Mutations are being discovered which, by themselves, are low-risk, but cumulatively make individuals highly susceptible to the environmental triggers for particular cancers.

Most of the supposed mutations have yet to be identified, but assuming they are, healthy adults or even children could be given "early warning" assessments about their likelihood of developing disease.

Sir Paul accepted that this kind of genetic fortune-telling was highly controversial, but felt the benefits would be seen to outweigh the drawbacks.

"I think, ultimately, the NHS, if properly funded, is going to be of enormous benefit in this area. The way we're talking about predicting disease is entirely incompatible with insurance for medicine," he said.

"If you can identify cohorts of the population which are more susceptible, the potential benefit is very considerable. But there are problems. How do you deal with diseases for which you can predict risk but have no way of treating?"

Sir Paul attacked the government for what he saw as its failure to deal with tobacco, which still causes 100-120,000 premature deaths a year, about half of them cancer.

"When you see how much fuss is made about cannabis and you see the number of deaths caused by tobacco, you just have to throw up your hands in disbelief," he said.

Advances in genetics are being monitored by the private health industry, but experts yesterday were doubtful about the impact of the developments on their businesses.

Stephen Sklaroff, deputy director of the Association of British Insurers, said: "Genetics plays a part but so many other things come into play, such as environment, what you eat, exercise.

"For that reason it's likely to be the case that for the foreseeable future the number of conditions where genetic test results would even be relevant for insurance conditions is going to be pretty small."

In 1998 the British insurance industry set up a code of practice that said insurers should not ask a client to take a genetic test before getting insurance.

Virginia Warren, associate medical director of Bupa, said it was possible that if more was known about a patient's predisposition to a disease, private health care providers could focus more on preventative services rather than treatment.

But Dr Warren believed people would still want the option of seeking private care. "Sir Paul seems to be suggesting a rather regimented society, quite a paternalistic society. People value choice. There's no reason to think that attitude will change. There will still be a role for private health care."