The row over badger culling in the South West has stepped up a gear this month with auctioneers in the region considering legal action against the Government in a bid to block a new TB-testing regime.

The move could seriously interrupt livestock markets as the pressure bites and although it will be a countrywide action, it is expected to hit Westcountry farmers the most.

Plans to force farmers to test cattle for TB before moving them off their land has already caused anger, and plans to test all cattle except those going directly for slaughter, are being challenged by the NFU. Now the Livestock Auctioneers Association has warned that the pre-movement testing could devastate the traditional markets that still formed the backbone of rural life in many areas.

New rules are due to come in on February 20 and it is felt they will seriously decrease the marketability of cattle, be almost impossible to implement and have little impact on the spread of bovine TB.

Defra insists pre-movement examination will work, and not only in the South West.

Auctioneers, however, feel the South West would be hit hardest and that many farmers would be unable, or would object, to paying for the tests and send more cattle directly to slaughter while others would simply give up cattle altogether.

But the bovine TB row is expected to spread into the supermarket. There have been suggestions by animal welfare groups of a butter boycott if farmers get the go ahead to cull badgers. Ian Johnson, South West NFU spokesman, said it would do nothing to prevent the spread of the disease and could end up hitting the farmer even more financially.

If bovine TB was left unchecked there would not be any cows left for butter to be produced, he said.

One South West badger group has said it will do "whatever it takes" to save animals if a cull was introduced.

Defra says that any culling would be carried out by farmers, but many say they would not carry out the culling for fear of recriminations.

A Defra spokesman told South West Farmer that TB in cattle was the biggest animal disease problem it faced, and the South West - and in particular, Devon - was badly affected.

Between January and November, 2005, 1,144 farms - almost 20 per cent of Devon's cattle farms - were put under restrictions at some point because of positive TB tests. In Cornwall, it was 635.

"Our assumption is that if a cull does go ahead it would be carried out by farmers, or their agents. Culling by the state is unlikely to be either efficient or cost-effective," he said.

Richard Haddock, a south Devon farmer, said Government ministers and Defra officials should visit the region to see how gassing of diseased badgers could be carried out humanely.

At a meeting of livestock dealers in Devon he said officials had already been shown via a fibre optic camera how it can be done. Now pressure should be put on them to get a trial underway in Devon.

* Westcountry beef producers will make consumers feel thoroughly sick if they persist with their demands for gassing badgers, warns the conservation group, the Badger Trust.

The warning follows a demand from the National Beef Association (NBA), which has told the Government that it wants farmers to be able to gas badgers with vehicle exhaust fumes. It was a move supported by livestock dealers and farmers when they attended a meeting in Devon. Tractor exhaust gas was a humane method of gassing, it was agreed.

But David Williams, chairman of the Badger Trust, said: "The public is supportive of farmers, but not at any price. There is even greater public support for animal welfare and nature conservation. Consumers are not going to appreciate the taste of British beef if it has been contaminated by the poisonous stench of gassing."

The NBA has told Defra that carbon monoxide gas must be included in a badger culling tool box and urgent government approval for it is essential.

It has said that those taking part in a cull must have good tackle at their disposal and that snaring or shooting are not enough on their own to provide an effective armoury.

"If carbon monoxide is used as the principal tool, and is backed up by other culling methods, the required culling intensity would be achieved," said NBA chief executive, Robert Forster.

"Exhaust gas from petrol engines already has a sufficiently high concentration of carbon monoxide and there are means of raising levels even higher."

"Over 30,000 cattle are expected to be slaughtered as a result of TB testing this year and their deaths could have been avoided. Also some £140 million could be spent on TB controls - with over £250 million a likely expense in 2010 unless someone in Defra grasps the culling nettle.

"This means there are overpowering public arguments to support the use of carbon monoxide as the principal tool when a culling programme is adopted."

But Mr Williams criticised Robert Forster for saying that the slaughter of 30,000 cattle with TB this year "could have been prevented".

Mr Williams said: "Robert Forster knows full well that the vast majority of the spread of bovine TB is down to the 14 million annual movements of cattle, not badgers.

"The spread of TB could have been prevented years ago, had the National Beef Association and other farming lobbyists not held the Government to ransom over badgers. We fully understand that farmers are upset at the spread of bovine TB, but the blame for that - as with other animal disease disasters - lies squarely at their own door. Bovine TB is a mess of farmers' own making."