It has become a widespread belief that the mapping of the human genome will lead to a new era of medicine. Shortly before the first drafts were published with great fanfare in February, Francis Collins, the director of the US National Genome Research Institute and a founder of the public-sector Human Genome Project, laid out a vision of a future in which mankind will call on unprecedented resources in the fight against disease.

By 2010, Collins predicted, scientists will have developed tests for dozens of genetic illnesses. A decade further down the line, there will be gene-based designer drugs for diabetes, hypertension, heart disease and schizophrenia. Cancer treatment will be transformed, and every patient will be prescribed medicines that are tailored to his or her own genetic fingerprint. In 30 years' time most Britons will live to the age of 90, and human beings will be able to manipulate their evolution by genetic engineering.

While some scientists quibble over the timescale of Collins's prognosis, few question the enormous potential of the genome to transform human life. Yet eight months after the project's success, many of its architects are raising concerns about the scientists' approach to realising its medical fruits.

They do not doubt the talent of the researchers in the field, and their ability to break new ground in the applications of genetics. But they fear that the profit motive has skewed priorities to an extent that will hold back research. Worse, they feel that it will alienate a public already sceptical of science, jeopardising our chances of exploiting the genome for the best.

Last Friday Sir John Sulston, the former director of the Sanger Centre near Cambridge, which sequenced a third of the genome, spelt out his concerns in the Chatham Lecture at Trinity College, Oxford. Much of genetic science, he said, was beset by a "new feudalism" of corporate sponsorship, in which basic researchers pay homage to their paymasters rather than seeking to expand human knowledge. The corporate drive for a piece of the genome manifests itself in a patent system that allows the privatising of whole genes, not just of the technologies that stem from their discovery. It has also been seen in the efforts of Celera, the Human Genome Project's private- sector rival, to restrict access to its data.

The brightest scientists, he says are being forced to work in the dark because of controls on basic research on which they must draw for new advances. Perhaps most worryingly of all, insurers and employers are seeking to shore up their profit margins with private genetic data, creating a climate of fear in a field that should brim with hope.

"Molecular biology as a whole is a revolution in thought just as profound as that of cosmology, which revealed to us our true place in the Universe, or that of evolutionary biology, which revealed our true place among living things," said Sir John.

"To understand our own bodies in minute detail, to understand how the instructions to make them are coded and applied, is an extraordinary philosophical advance as well as a practical one. Yet many people feel uncomfortable about that knowledge. With understanding comes the power to control and to alter. And it is here that we should pause and consider, for with power comes the responsibility to apply discoveries wisely."

If this responsibility is not met, he says, public support for scientists' work will evaporate, leaving both poorer. And the marketplace is insufficient to meet it. A case in point is genetic screening -a technology with tremendous potential for good, which is nevertheless among the most distrusted of the genomic age.

"We do not want a situation in which people are reluctant to be tested for fear that the information will be used against them by an insurer or an employer," he said. "Of course, the data is kept confidential, but since there is no such thing as a secure database, it is important that in the long run we do not depend on keeping patients' records secret but ensure in law that nobody can be disadvantaged by their genotype.

"An added reason for doing so is that we all share 50 per cent of our particular variations with our nearest relatives -parents, siblings, or offspring -so information about one member of a family immediately provides probabilities about the others. Privacy is not enough: we must outlaw genetic discrimination of any kind under human- rights legislation, just as has already been done for the well-known genetic characteristics of gender and race."

Sir John suggests that without such a move, science, as well as society, will lose. The supply of volunteers for clinical trials, without which no therapy, genetic or conventional, can be brought to market, will dry up. If insurers will not wear such measures, and the Government accepts their case, it must step in, much as it did for airlines after September 11, as an insurer of last resort.

Patent law, too, needs reform. The system has allowed companies and institutions to protect not only the therapies that emerge from genetic research, but entire genes. This is not only wrong -another factor provoking public distaste -but is also restricting science.

Sir John's colleague Mike Stratton, of the Cancer Genome Project, is having to battle over a gene that he discovered but which has patented by a US company. Scientists and companies that apply for patents are often highly secretive about their work. Sir John said: "They claim that business is business, but it is reducing the possibilities for research, and ultimately for cures."

The "new feudalism", he added, was largely to blame. "Confusing discovery and application has led to a widespread distrust of science because of the real and perceived lack of democratic control over application.

"The problem has been greatly exacerbated, and perhaps largely caused, by the profit motive. So much of research nowadays is paid for on the basis that profitable discoveries will be made that it tends to be taken as a given that exploitation will follow as quickly as possible on discovery. Of course, if there are good things to be done with the work, we should get on with them, but not in secret and not without heed to the consequences."

Sir John, who was knighted in the New Year Honours, has now retired from the genome project, and will expand on his case in a book written with Georgina Ferry, The Common Thread: A Story of Science, Politics, Ethics and the Human Genome, to be published in February.

Scientists must step back a little if the most is to be made of the genome, he argues. While private enterprise has a valuable role to play in realising the future portrayed by Collins, it cannot do so alone, or without allaying the proper concerns of ordinary people.

"The genome is not a Pandora's box -it is a genuine treasure chest," Sir John said. "But to open it fully, we need to have a rethink, to bring the public with us. The process must be democratic. It cannot be every man for himself. This is our common genome, and we must make common cause."

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