New research by environment ministry Defra suggests only one in seven badgers found dead at roadsides in the South West had tuberculosis.

Defra's badger road traffic accident survey was based on TB tests carried out on road-kill badgers.

It has been carried out in seven counties for the past three years.

But animal health minister Ben Bradshaw welcomed it, saying it showed "no clear correlation between levels of TB in cattle and badgers".

The traffic accident survey was designed to establish whether the level of bovine TB infection in dead badgers, collected from road accidents, reflected disease prevalence in the badger population in the area.

This was done by comparing data with findings from the randomised badger culling trial (RBCT).

The survey was carried out in the RBCT counties of Cornwall, Devon, Gloucestershire, Herefordshire, and Worcestershire. Shropshire and Dorset were also included as comparison counties.

The data collected was then used to estimate prevalence at county level.

In general, the prevalence of TB infection in badgers was higher in the northern group of counties involved (Gloucestershire, Herefordshire, Shropshire and Worcestershire) than those in the southern group (Cornwall, Devon and Dorset), the survey concluded.

The National Farmers Union says badgers should be culled, blaming them for the spread of bovine TB. Defra accepted that the survey was limited because not enough badgers were collected to give findings at a parish level.

However, animal health minister and Exeter MP Ben Bradshaw welcomed the publication of the data. He said: "These findings show that even in those parts of the country worst affected by bovine TB, most badgers test negative for the disease.

"They also show no clear correlation between the levels of TB in cattle and badgers.

"These latest findings will be used alongside other research and advice from the UK and abroad to develop policy on tackling bovine TB."

The survey was carried out on the advice of, and supervised by, the Independent Scientific Group on Cattle TB. The South West is already one of the hot spots for bovine TB in the UK. In Cornwall alone, between 1 January and 31 May, 250,000 cattle were tested and 1,500 animals slaughtered.

In Devon, 860 farms have suffered TB in cattle at some point this year.

Badger groups claim bovine TB is spread by cattle movements.