County Durham and Tees Valley contains the highest proportion of obese people in England, according to Department of Health figures.

Well over one in four adults in the area had a body mass index of more than 30 - the crude calculation for measuring the condition - in 2000-02.

The 27.3% figure for the strategic health authority area is nearly six percentage points worse than the national average of 21.4%. In the mid-90s, the area recorded 16.5%, the then national average.

That shift in an area which includes the prime minister's constituency could be politically embarrassing, because tackling obesity is a government priority. Ministers have proposed programmes to get people to exercise more and showe moderation in eating fatty and salty foods.

Comparisons between the 28 strategic health authorities in the survey, released under freedom of information rules, were previously intended for health professionals.

The figures show North and East Yorkshire and Northern Lincolnshire SHA to be second worst (26.1%), followed by Trent (25.1%) and the Birmingham and the Black Country authority (24.9%). The Birmingham SHA has been a consistently poor performer - it was the worst area in England at 20.4% in 1994-96.

Body mass index is calculated by dividing a person's weight in kilograms by the square of his or her height in metres.

Professionals say the figures are based on relatively small numbers of interviews followed by clinical assessments by nurses in each authority, so changes may be exaggerated.

But the purpose of the exercise, conducted for the government by the independent National Centre for Social Research in London, was to demonstrate public health trends at SHA level, and for the authorities to act on them.

It compounds the suspicion that the priorities of local management are not always the same as those in Whitehall.

But tackling the obesity crisis depends on the attitudes of GPs, community health workers, NHS managers and local authorities at primary care level, far smaller units than the strategic health authorities.

Dr Foster, an independent organisation which monitors healthcare, recently suggested that three-quarters of primary care organisations did not monitor the prevalence of obesity and nearly half did not make prevention or treatment a priority. Seven in 10 general practices had not established weight management clinics.

Parts of County Durham and Tees Valley are socially deprived and the area has scored poorly for years in the percentage of patients with long-standing illness, smoking, and drinking. But the SHA's slide on obesity contrasts with some success elsewhere in battling rapidly rising trends nationally.

Comparisons with the 1994-96 figures indicate that health service workers in South-East London SHA have had some success in at least stabilising obesity. Once regarded as an authority with high levels - 19.1% in 1994-96, well above the then average - it now has 19.2% of over-16s obese, well below the present average.

That makes it the seventh-best performer. The area with the lowest percentage, 12.3%, in 1994-96, Leicestershire, Northamptonshire and Rutland, now comes sixth in the league with 24.3%.

David Haslam, a Hertfordshire GP who chairs the National Obesity Forum, said: "Some primary care trusts and groups of PCTs have amazingly good strategies for tackling obesity. Others have no strategy at all, don't allow the use of drugs, don't have access to surgery. There are deserts where management is poor."

From best to worst - Estimated percentage of over-16s obese

England total 21.4
County Durham and Tees Valley 27.3
North and East Yorkshire and N Lincolnshire 26.1
Trent 25.1
Birmingham and the Black Country 24.9
South West London 24.3
Leicestershire, Northamptonshire and Rutland 24.3
Kent and Medway 23.1
Shropshire and Staffordshire 22.9
West Midlands South 22.6
Cumbria and Lancashire 22.4
Norfolk, Suffolk and Cambridgeshire 21.6
Hampshire and Isle of Wight 21.4
Northumberland, Tyne & Wear 21.3
Greater Manchester 21.1
Cheshire & Merseyside 21
West Yorkshire 20.8
North East London 20.7
Essex 20.2
South West Peninsula 19.9
South Yorkshire 19.6
Dorset and Somerset 19.3
South East London 19.2
Thames Valley 18.9
Bedfordshire and Hertfordshire 18.8
North West London 18.4
North Central London 18.4
Surrey and Sussex 17.6
Avon, Gloucestershire and Wiltshire 17.3

· Source: Health survey for England