In 1991-92, the first year of the changes, the number of finished consultant episodes - the approximation for patients treated - rose by 7.3 per cent, figures released yesterday show. Spending that year, in the run-up to the general election, rose by 6.6 per cent in real terms.
Last year, patient treatment numbers rose by 4.3 per cent, with a spending increase of 5.5 per cent, while in the current year, when spending has risen by 3 per cent, the number of patients treated is expected to rise by 3.5 per cent - half the rate of two years ago.
The NHS now faces 'a new challenge to maintain the momentum' he said, after a period when increases in the numbers of patients treated have 'outstripped anything we saw before the reforms'. In the 1980s, the increase in numbers treated averaged 2 per cent.
Next year ministers are hoping for a 4 per cent rise in activity on the back of the 1.4 per cent rise in spending announced in the Budget. That will depend on the level of pay rises and on efficiency gains of 2.25 per cent - the highest the NHS has ever been asked to produce.
Launching last year's health service annual report, Sir Duncan said the NHS had treated more patients than ever (nearly 8 million); had cut waiting times and become more cost-effective partly because of a switch to day surgery, from 38 per cent of non-urgent cases to a forecast 45 per cent this year.
David Blunkett, Labour's health spokesman, argued the report was out of date, with figures showing a 25 per cent rise in numbers waiting more than a year for treatment.
The new figures come as Sir Duncan confirmed that league tables of hospitals' performance will be published in June after agreement with the Audit Commission on how they should be compiled.