Managers leading trusts named as the most expensive in the country have accused league tables published this week of not comparing like with like.

David Dalton, chief executive of Walton Centre for Neurology and Neurosurgery trust, which topped the national reference cost index, published for the first time on Monday, said: 'The nature of neurosurgery means high technology in both diagnostics and treatment.

'It is difficult to draw the conclusion we are an expensive provider when neurosurgery is all we provide. We are proven to be cost- effective.'

Neil Chapman, director of finance at United Leeds Teaching Hospitals trust, branded the second most expensive provider, said the trust had only been formed in April.

'As a result of the reconfiguration, there will savings of£10m over the next two and a half years. This should bring us back into the mid- range.'

Health minister Alan Milburn promised to establish a system of national reference costs shortly after taking office to 'enable trusts to find out how efficiently they are performing compared to similar trusts'.

The first national schedule of reference costs covers 500 surgical procedures involving£5bn of NHS spending. It was compiled from information supplied by all 249 trusts delivering acute care in England.

It shows that the cost of standard operations varies widely, with the cost of a hip replacement varying from£1,834 to£6,494, with an average cost of£3,678.

The national reference cost index, released at the same time, consolidates the cost of individual procedures to 'compare how hospitals perform on cost across all surgical procedures'.

Health minister Alan Milburn described the discrepancies as 'unexplained and unacceptable', and warned that high-cost hospitals would face 'tough new efficiency targets' to tackle both cost and quality.

But the index shows that although the lowest cost trust is about 30 per cent below average and the highest 60 per cent above, nine out of ten trusts fall within 20 per cent of average.

Paul Lumsdon, general manager of hospital and community nursing at Dorset Healthcare trust, which came second from bottom in the table said: 'We are a small, friendly community hospital with low overheads, nothing like a large acute trust.'

Kent and Canterbury trust chief executive Jim Smith said it was 'highly delighted' to be named as joint third cheapest trust, but pointed to high levels of day surgery as an important factor.

He stressed that the trust's general district and teaching hospitals 'do not compromise the quality of their work to achieve cost savings'.

But the Institute of Health Services Management warned against focusing on costs 'at the price of patient care', while the NHS Confederation attacked the government's approach of 'blame, rather than partnership'.