Britain's system for monitoring cancer trends could collapse if new guidance from the General Medical Council is implemented, warn researchers.

The guidance, intended to protect patients' confidentiality, says doctors should not transfer individuals' details to cancer registries without their consent. But the GMC's critics say that the guidance is unworkable and that most clinicians will stop registering data.

The guidance, dated June 2000 but issued in September, came just before the government pledged in its National Cancer Plan to improve Britain's cancer survival rates to equal the best in Europe.

But Dr …