The erosion of data will almost certainly lead to an increase in cancer deaths unless action is taken quickly

Professor Gordon McVie, Cancer Research Campaign

Researchers say that in some cases, particularly statistical research involving thousands of patients, it is impractical to seek consent from every one, particularly as the question will have to be posed just as the patient receives devastating news about their health.

Common law on confidentiality suggests that patients should be asked for consent before any private information is passed on, and the arrival of the 1998 Data Protection Act reinforced the need for the medical profession to follow these principles.

When the General Medical Council (GMC), which regulates doctors issued fresh guidance last year echoing all this, many hospitals immediately stopped sending vital data to the registry.

All cancer cases should be reported to a national registry

The GMC, seeing the chaotic response to the guidance, delayed its introduction until October this year, but many predict that exactly the same thing will happen again at that point.

Dr Richard Foreman, who oversees the registry in one English region, said: "Within days of the guidance being published, trusts were refusing to pass on information about cancer patients.

"If this continues, we will no longer be able to look at trends, no longer able to investigate "hotspots" of cancer - or check the progress of the government's own national cancer strategy."

Professor Gordon McVie, the director general of the Cancer Research Campaign, said: "The erosion of data will almost certainly lead to an increase in cancer deaths unless action is taken quickly."

GMC blamed for chaos

Some doctors believe the present crisis is the fault of the GMC's guidance, which they say is far more Draconian than it need be.

Professor Michel Coleman, from the London School of Hygeine and Tropical Health, said: "Medical research that saves lives is directly threatened by this poorly-conceived guidance.

"It undermines our ability to improve understanding of the causes of disease, identify the best treatments, and pick out regions of the country where disease outcomes are poor, for remedial action."

We have to advise doctors to act within the law

Professor Hilary Thomas, GMC

He said that while the impact on the cancer registry had been instant and obvious, research into many other areas, such as heart disease, mental illness and Parkinson's disease were vulnerable.

Researchers want the government to make the supply of data about cancer patients compulsory in the same way that information about notifiable diseases such as TB is collected, rather than subject to the consent of the patient.

An amendment to the government's Health and Social Care Bill setting up a body too look at the issue and advise ministers is likely to be debated in the House of Lords on Thursday.

The GMC is resisting calls for it to revise the guidance.

'Shoot the messenger'

Professor Hilary Thomas, a consultant oncologist who chaired the committee which drew up the guidance, said: "We feel this is a classic case of 'Shoot the messanger'.

"We have to advise doctors to act within the law - we feel our guidance has been misrepresented."

Professor Thomas said that some current methods of data collection might well be questionable - for example, computerised results from hospital pathology departments are instantly sent to the cancer registry - meaning the data has left the hospital before the patient has even learned of their diagnosis.

She said she felt it was the role of government to decide whether the benefits to public health research of passing on data without consent outweighed the rights of the patient to have a say.