Campaigners have reacted angrily after it emerged that badger culls could be extended by three weeks because not enough animals have been killed.
The culls in west Somerset and Gloucestershire could be extended to maximise the impact on the spread of bovine tuberculosis, Environment Secretary Owen Paterson revealed.
Mr Paterson said the six-week action in west Somerset has killed 850 badgers - 60% of the local population.
"Current indications suggest that the pilot has been safe, humane and effective in delivering a reduction in the badger population of just under 60%.
"We set ourselves a challenging target of aiming to ensure that 70% of the badger population was removed during the pilot. The chief veterinary officer (CVO) has advised that the 60% reduction this year will deliver clear disease benefits as part of a four-year cull.
"However, Natural England are considering an application from Somerset for a short extension of the culling period, as provided for under the agreement with the company.
"The advice of the CVO is that further increasing the number of badgers culled would improve those benefits even further and enable them to accrue earlier."
He added in a statement to MPs : "The cull in Gloucestershire is still ongoing and I will make a further statement when the six weeks is completed. I understand that this morning Gloucestershire is also submitting an application for an extension to Natural England."
Mr Paterson indicated that in future the period for culls may have to be longer than six weeks to ensure "high levels of safety and humaneness".
"This Government is committed to tackling the disease in all reservoirs and by all available means. Our cattle industry and the countryside deserve no less," he added.
But Queen guitarist Brian May, a leading opponent of the cull, said figures showing the number of badgers killed were "widely disparate", and urged ministers to abandon the "ridiculous" cull.
He told BBC Breakfast: "To be honest, it's getting more and more ridiculous. This is the third lot of figures we've seen, they're widely disparate.
"They have no idea how many badgers there are and they keep adjusting the figures to make it look like this is a success.
"This was supposed to be a two-week shoot. It's already been extended to six weeks from two - now they want another three weeks.
"This has demonstrated already that free shooting doesn't work. The only way they got to 800 badgers was by cage-trapping and shooting.
"If you are cage-trapping and shooting, you can cage-trap and vaccinate.
"There is no way on earth that culling badgers can lead to the eradication of TB.
"We have to abandon this ridiculous cull.
"This cull is a waste of time and a waste of our money."