Sustaining the National Health Service over the next 20 years will be made harder by the poor state of the British population, an interim report by Derek Wanless shows.

Life expectancy at birth is low in England compared with other countries, and mortality rates for some of the main chronic diseases such as cancer and heart conditions are high. Mr Wanless is leading an independent study looking at health trends and assessing their likely long-term effect on the NHS. The results of his work are crucial in determining the potential cost of the health service to the public purse.

There are large gaps in health between Britain's rich and poor and big differences between ethnic groups, which contribute to the country's dismal showing internationally.

The first Wanless report, published last year, said the NHS should continue to be funded from taxation and described three possible scenarios, depending on how health improved.

If the best case scenario is attained, the report suggests that the cost of the NHS could £154bn a year instead of the £184bn it will cost should the present poor levels of health and inefficiency in the health system remain.

But Mr Wanless' interim report shows how difficult it will be to achieve the best scenario. It compares the main causes of mortality in Australia, Denmark, Canada, Finland, France, Germany, the Netherlands and Sweden - countries selected because they have similar population profiles, wealth and health systems to the UK.

It shows that deaths from respiratory diseases in Britain are at least 50 per cent higher among women and 30 per cent higher among men than in all other countries.

Britain tops the table for infant mortality, which is 70 per cent higher than in Finland. Cancer deaths among women are second only to Denmark and the UK is ranked 25 per cent higher than in France.

British women are in general less healthy than those in the other countries with lower life expectancy and higher numbers of premature deaths before 70. On heart disease Britain is better than Germany and Finland but worse than the other six countries for both sexes.

Professor Sian Griffiths, the president of the Faculty of Public Health, said: "We have got a long way to go on prevention to make a difference. The Government has been so focused on short-term measures to cut waiting lists that it has not invested in prevention. We need research to show what works and we need all clinicians to take prevention seriously. The Government has to act on the key issues, such as smoking and obesity."

Professor John Britton of the British Thoracic Society said Britain's high death rate from respiratory diseases, more than 50 per cent above the comparator countries, was "a real shock".

He added: "Cutting smoking radically is the big thing that would make a difference. In the longer term, clean atmospheres, a better infant and adult diet and reductions in obesity would have an impact."

Richard Brighton of the British Medical Association's public health committee said Britain's poor performance was due to wide social class differences. The wider the gap between top and bottom incomes the greater the burden of poor health, he said. "This is not about specific diseases but the way our society works. One aspect that Wanless is not looking at is the tax system. We need to recognise that the tax system does have a health impact."

The final Wanless report, due in the spring, is expected to recommend sweeping measures to reduce the burden of ill health caused by obesity, smoking and other factors in order to lessen demands on the NHS and achieve the best spending scenario over the next two decades.

John Reid, the Health Secretary, said: "The Prime Minister, the Chancellor of the Exchequer and I asked Derek Wanless to look at health trends in this country precisely because we know there are glaring inequalities between areas.

"This report provides a valuable snapshot of the current picture and some useful comparisons with other countries. It will be a key tool in ensuring the extra investment we are putting into health improvement is well spent."

Mr Reid continued: "It is also worthwhile considering recent mortality trends, as shown by the World Health Organisation figures between 1990 and 1999. They show, for example, that the 18 per cent reduction in United Kingdom cancer mortality rates was greater than in the countries examined in Derek Wanless' report.

"And the 41 per cent reduction in the mortality rate from coronary heart disease in those under 65 is well above the 31 per cent fall in the EU as a whole," he added.