The guidelines, publised by The Association of Anaesthetists of Great Britain and Ireland, emphasise the importance of effective two-way communication between practitioners and their patients, rather than simply obtaining a signature on a consent form.

The guidance provides advice to anaesthetists on the appropriate information to give to patients about anaesthesia and its potential risks.

It also recommends that a record should be made of the discussion with the patient and the information given.

At present, there is some uncertainty among anaesthetists regarding the requirements for obtaining consent for anaesthesia, and the aim of the guidance is to provide a clear way forward to ensure that patients are well informed.

Professor Alan Aitkenhead, chairman of the Association's Consent Working Party, said the guidelines had become necessary because lawyers were increasingly including allegations about lack of consent in claims for negligence.

Until now, most anaesthetists operated a policy that explanation was unnecessary in cases where the risk to the patient was assessed at less than one per cent.

Professor Aitkenhead said: "Every patient sees their anaesthetist before their operation.

"This guidance states that the anaesthetist must tell them what will happen before, during and after they have been anaesthetised. There must always be opportunity for questions.

"On the other hand, we must strike a balance. Anaesthesia is highly complex - so we do not recommend that every risk of every component of the anaesthetic technique should be explained.

"We believe that this would need presentation of a bewildering quantity of information. This could lead to patients making choices about small components of the overall procedure which may harm their safety."

Research consent

The guidelines will be distributed to all members of the Association and Departments of Anaesthesia.

They provide advice for anaesthetists managing children, the mentaly ill, women in labour, those with beliefs that forbid certain clinical procedures and those wilth advanced directives.

They also provide guidance for obtaining consent for research and the use of new drugs.

There are 8,100 anaesthetists in the UK, who are involved in the care of two-thirds of all hospital patients.

As well as preparing patients for surgery, they are involved in acute and chronic pain management, leading resuscitation teams and managing intensive care units.