The devolved administrations have pursued different policies
The NHS in England provides better value for money than elsewhere in the UK, a research group's study suggests.
The Nuffield Trust found there were fewer health staff per head in England, but higher levels of activity and productivity, as well as shorter waits.
The differences were most marked when England was compared with Scotland, but there was nothing to suggest major variations in quality of care.
Health officials in Scotland said the comparison was unfair and out-of-date.
It is the first time experts have carried out such an analysis of NHS efficiency and it comes at a time when the health service is facing a squeeze on its funding in the coming years.
The independent research group compared a range of factors over a 10-year period to 2006-7.
It found that the NHS in England spends less and has fewer doctors, nurses and managers per head of population than the health services in the devolved nations, but is still doing more.
At the time studied, England was the only part of the UK in which patients needing operations had to be seen within six months.
Hospitals in England now see all patients within 18 weeks. The rest of the UK is still some way from that point with Scotland not expecting to hit it until the end of 2011.
Productivity levels fell across the UK during the period - something which is already well documented.
But those falls tended to be most marked in Scotland with the NHS there providing the fewest outpatient appointments, inpatient admissions and day case treatments per doctor of all the parts of the UK.
To take into account the economies of scale and different levels of deprivation between the different parts, the report also looked at individual English regions.
Even when Scotland was compared to the north east, which has similar levels of health need and poverty, the differences were even more marked.
However, the research did not carry out a detailed analysis of quality of care.
It is in any case very difficult to make a fair comparison between the four nations since they collect different data in different ways
Patient satisfaction rates were compared but these were broadly similar. Meanwhile, a more in-depth analysis of quality of care last year by a different set of researchers found no significant differences.
Dr Jennifer Dixon, director of the Nuffield Trust, said the latest findings posed "challenging questions", particularly in the current economic climate.
She added: "Some of the differences and trends may be because of the historical differences in funding levels, which are not directly related to policies implemented after devolution.
"But some will reflect the different policies pursued by each of the four nations since 1999, in particular the greater pressure put on NHS bodies in England to improve performance in a few key areas such as waiting and efficiency, via targets, strong performance management, public reporting of performance by regulators and financial incentives."
But Scottish Health Secretary Nicola Sturgeon said the comparison was unfair and out-of-date, pointing out many of the measures had improved since the study was carried out.
Jennifer Dixon, Nuffield Trust: "In England there's been a tougher approach to performance management."
She added: "Some of the challenges NHS Scotland faces are unique certainly in a UK context such as some of the more deep-seated issues of deprivation and ill health and of course our dispersed geography.
"Now these are not excuses for bad performance, but they do mean that it is not always possible to make crude comparisons between one part of the UK and another."
A spokesman for the Department of Health in England said the findings were a "testament to the tremendous hard work and achievement of NHS staff".
He added ministers were looking to "build on the strong performance".
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