Chief medical officer Sir Kenneth Calman used his final annual report to question the value of some of the 100 screening programmes in place across the NHS.

'I suspect some of them are not necessary and do not have the right quality,' he said last week. 'We need to get rid of the ones that we do not need and improve the ones we do.'

Sir Kenneth would not give examples of failures but said those with a record of success, such as breast, cervix and neonatal screening, could be improved.

The National Screening Committee, set up in 1996, is studying the 'efficacy and feasibility' of screening for diseases such as chlamydia, cystic fibrosis, Down's syndrome, fragile X syndrome and ovarian cancer.

A series of pilot screening studies are planned, starting with a two- site, 2.5m colorectal cancer project announced last Thursday.

This will cover 1million people in England and Scotland to gauge whether a national screening programme is feasible and acceptable to the public.

Public health minister Tessa Jowell said the pilots would 'break the taboo' of bowel cancer, which is 'one of the most curable of all cancers' if caught early.

Sir Kenneth also called for more effective treatment and intervention in non-insulin dependent diabetes mellitus.

This currently affects 1 million people in the UK, but could affect 3 million by 2010.

Diabetes and its complications account for 5 to 10 per cent of hospital costs - 1.4bn at 1996 prices. Sir Kenneth said selective screening among Asian and African communities, the elderly, the obese and those with a family history of the condition could prevent serious problems.

Sir Kenneth, who is stepping down after seven years as CMO, said life expectancy and quality of life is on the rise except in the 15-44 age group.

Young men still have a higher death rate, despite a fall in the suicide rate.

In a characteristic touch, Sir Kenneth said people should read the popular novel Trainspotting to find out why. His final report devoted a chapter to the environment and the potential health problems associated with global warming.

'There has been increasing awareness of the interconnection between our environment and quality of life and that changes in environment may lead to ill health,' Sir Kenneth said.

The long-awaited report on health inequalities by Sir Kenneth's predecessor, Sir Donald Acheson, which will play a key role in shaping the public health white paper, is due out by the end of the year.

The incoming CMO, Professor Liam Donaldson, may note what Sir Kenneth called 'adverse trends in some key determinants of future disease'. These include obesity, cigarette smoking, alcohol consumption, sexually transmitted disease and under-age pregnancy, and excessive winter mortality.

On the State of the Public Health 1997. The Stationery Office. 18.50.