Up to 50,000 badgers could be killed this year under the government’s controversial culling scheme – nearly double the number of last year and three-quarters of the total killed since the cull began six years ago, campaigners claim.

The increase is caused by a predicted expansion in licensed culling zones – areas where farmers can exterminate badgers, which are blamed for spreading TB in cattle.

This week the government is expected to confirm that a further 10 zones in England are to be approved, taking the total to 42. But the announcement is likely to clash with data released under the Freedom of Information Act, that suggests incidents of bovine TB may be increasing in cull zones, which would make it difficult for the government to justify expanding the cull.

And, in a sign that Boris Johnson’s government is more ambivalent than its predecessor about the cull, it has emerged that a potential licence for a culling zone in Derbyshire – where vaccination of badgers against TB has been taking place – was withdrawn last Friday.

Dominic Dyer, chief executive of the Badger Trust, claimed prime minister Boris Johnson’s father, Stanley, and the PM’s partner, Carrie Symonds, both animal welfare campaigners, oppose the cull and have influenced Johnson’s thinking.

Dyer warned him: “Your government is about to sign off on the largest destruction of a protected species in living memory – as you are aware nearly 68,000 badgers have been killed in England since 2013, in a failed attempt by the government to lower bovine TB in cattle.” He added that the expansion of the culling zones “could result in the killing of over 50,000 badgers in the next two months, pushing this protected species to the verge of local extinction in areas of Britain it has inhabited since the ice age”.

Your government is about to sign off on the largest destruction of a protected species in living memory

There are unconfirmed claims that, in a potential breach of the law, badgers are being killed in some of the zones before the licences have been issued. The culling season lasts from mid-September to the end of November. Last year 28,000 badgers were killed – either by being lured out of their setts with bait and then shot, or by being lured into cages and shot – in 32 areas across England.

A Defra spokesman said it wouldn’t comment on the issuing of new culling licences, and the ultimate decision was taken by Natural England, the government’s advisory body.

New research to be released tomorrow, based on official data and produced by a group of leading vets and academics spearheaded by the former government scientist Iain McGill, shows that confirmed incidents of bovine TB in the Gloucestershire culling pilot zone rose by 130% in 2018 compared with the previous year.

This undermines claims made by Theresa May’s government that cases of bovine TB had reduced in Gloucestershire since the cull was introduced six years ago.

A spokesman for the National Farmers Union, which supports the cull as part of a range of eradication measures, said: “Bovine TB continues to devastate family farming businesses across large parts of the country. Last year, nearly 33,000 cattle were slaughtered in England because of this terrible disease and more than 3,600 farms that had previously been clear were affected by it.”

Defra said the disease costs the taxpayer £100m a year. In 2018 more than 32,000 cattle were slaughtered in England to control the disease.

“Bovine TB remains one of the greatest animal health threats to the UK, causing devastation for hard-working farmers and rural communities,” a Defra spokesman said.