Farmers will be issued with licences to cull badgers in a bid to stamp out bovine tuberculosis (bTB), despite fierce opposition from campaigners.

A senior source at the Department of the Environment, Food and Rural Affairs (Defra) has said the move will go ahead despite the protests of those who see badgers as something from "Beatrix Potter" books and harmless "Wind in the Willows" characters — because it is the "right thing to do".

Environment Secretary Caroline Spelman will give the green light for the cull to go ahead in parts of the South West, the region worst affected by bTB, it was claimed.

Ministers fear the disease is now spreading beyond isolated rural areas, posing the risk of it travelling even faster and infecting domestic animals.

It is understood by the Western Daily Press that licences are expected to be issued in May 2011.

A senior Defra source said that the move was bound to spark the kind of protest seen in Wales, where the Badger Trust successfully launched a legal bid to halt a cull.

The backlash is expected to be considerably stronger in England, because the exercise would be on a much larger scale.

The source said: "This will not be popular with people who view badgers as something from Wind in the Willows or Beatrix Potter, but it is the right thing to do. We cannot go on not taking action to deal with this huge problem."

But the official Defra line is that proposals for a cull are still being developed and a consultation process will be launched in the coming weeks.

Last year alone, 25,000 cattle were killed as a result of bTB, and the annual cost to the taxpayer now exceeds £100 million.

In the West farmers are convinced badgers are the source of the spread of the disease, and say culling vast numbers of cattle has done nothing to stem the flow.

Jilly Greed, South West spokesman for the National Beef Association, said the latest news was encouraging for cattle farmers.

"If this is the case, it's really heartening for beef and dairy farmers who are under restriction, and currently seeing no hope of a solution.

"It's evident that without tackling the reservoir of disease at source, we are completely plunged into a no man's land where there's just perpetual TB, and so some common sense is coming through here, backed up by science."

But Ian Johnson, South West spokesman for the National Farmers' Union, said members would only get excited when there was an official announcement on the cull.

He said: "The source at Defra is pointing out the obvious when he says it's the 'right thing to do', but the tragedy is that it has taken officials so long to come to that realisation."

Yesterday, a Defra spokesman refused to confirm that the cull would go ahead.

He said: "The Government has committed, as part of a package of measures, to develop affordable options for a carefully managed and science-led policy of badger control in areas with high and persistent levels of bovine TB.

"We are currently developing proposals which we plan to publish for public consultation in the coming weeks."

Jack Reedy, spokesman for the Badger Trust, said: "The Appeal Court recently upheld the Badger Trust's challenge to the Welsh Assembly government's proposal to kill badgers as unlawful.

"Such killing in a attempt to control bovine TB is also likely to make matters worse, and it would be seriously bad news – chiefly for the farmers themselves – if any licences were issued anywhere."

The previous Labour Government relied on vaccination as the answer to stopping the spread of TB. But former Government chief scientist Sir David King is among those who believe that culling has a role to play.

However, the Badger Trust and its supporters rely on a 2008 report by the Independent Scientific Group on Cattle TB, which concluded that culling would not "meaningfully contribute" to tackling the disease.

Farming Minister Jim Paice has stressed that plans for a cull must be legally watertight, to ward off any court challenge.