Badgers 'moved goalposts' says minister Owen Paterson
A government minister said "badgers moved the goalposts" when asked why marksmen failed to reach a cull target.
A pilot badger cull in west Somerset may be extended by up to three weeks in an effort to make up the shortfall.
Environment Secretary Owen Paterson was asked if he had "moved the goalposts" by claiming the cull was a success.
However, those behind the cull itself were denounced as "incompetent", in the House of Lords.
Mr Paterson explained difficulties lay in the fact the operation was dealing with a wild animal.
"The badgers moved the goalposts. We're dealing with a wild animal, subject to the vagaries of the weather and disease and breeding patterns," he said.
The pilot culls in Gloucestershire and Somerset set out to study if badgers could be killed safely, effectively and humanely.
They are being carried out in an attempt to control TB in cattle, which can be spread by badgers. Opponents say they will have no impact.
'Reduction in disease'
The plan was to kill 70% of badgers in the areas of west Somerset and Gloucestershire by free shooting.
Across both regions this meant around 5,000 badgers were to be killed in total.
But Defra sources said these targets were based on population estimates from 2012 that have proved to be highly inaccurate.
In west Somerset, the population, which had been estimated at 2,400, has now been revised downwards to 1,450. In Gloucestershire, the numbers have been lowered from 3,400 to 2,350.
In a written statement to MPs, Mr Paterson said: "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.
"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."
But Queen guitarist Brian May, a leading opponent of the cull, branded the approach an "utter failure" and described the application for an extension as a "farce".
"It's a failure because they said they had to cull 70% and they failed to do that. They are now applying for an extension," he said.
"This is becoming a farce. They are now being told that probably the prevalence (of TB) has increased in badgers already.
"They were warned this would happen and they did not listen to the scientists."
During an urgent question in the Lords, independent crossbench peer Robert, Lord May of Oxford, said the government had ignored expert opinion.
"This cull went ahead against the balance of advice from the scientific community in particular that a limited experiment such as this was unlikely to yield much in the way of useful information," he said.
He asked environment minister Lord de Mauley: "Would you agree with me, however, that we have indeed learned something important?
"We have learned that those responsible for this so-called experiment are so incompetent that they couldn't even make a reliable estimate of the number of badgers."
Lord de Mauley disagreed, saying the policy followed was "evidence-based".
"We have taken every opportunity to acquire the latest and most up-to-date information from the pilot areas to refine the estimate of the badger population," he said.