Electro-convulsive therapy (ECT) should only be used to treat people with mental health problems as a last resort according to new guidelines issued by National Institute for Clinical Excellence.

NICE has recommended that ECT should be restricted to patients with severe depression, catatonia and prolonged or severe manic depression.

Chief executive of NICE, Andrew Dillon, said that the guidelines "will help patients, and those who treat them, better understand the benefits and risks of ECT and in doing so reduce the uncertainty surrounding the use of what has been a controversial technique".

The institute said that ECT should only be used in the short-term when other treatments, such as medication and psychotherapy, had proved ineffective. The guidelines also state that doctors must warn patients of the potential side effects of ECT, which include memory loss - and in rare cases facial paralysis - and ensure that they consent to the treatment where possible.

The mental illness charity Rethink welcomed the new guidelines. Paul Corry, head of policy at Rethink, said: "NICE has recognised that ECT has no proven benefits in the general treatment of schizophrenia. ECT is controversial largely because it has a long and undistinguished history of being imposed on people against their will in circumstances that fall well short of modern medical practice."

ECT patients first receive a general anaesthetic and a muscle relaxant before a current is administered via electrodes for three to four seconds. This provokes an epileptic seizure, which is supposed to restore the natural chemical balance of the brain.

But the Royal College of Psychiatrists believes that the guidelines are too restrictive. Dr Allan Scott, a member of the college's special committee, said "at least 30 per cent of patients with depression will be denied a potentially valuable treatment".