Almost 10,000 experiments were conducted on animals, including monkeys and pigs, at a top-secret military research facility last year.
The number of animal tests carried out at the Porton Down increased by 300 since 2010 and by more than 1,000 since 2009.
Porton Down research facility in Wiltshire
Currently 21 licensed animal procedures are under way at Porton Down Defence Science and Technology Laboratory (DSTL).
Most of these fall into the "substantial" severity category which may cause "significant or prolonged animal suffering".
Six of the projects cover work funded directly by US defence agencies.
The details were disclosed in a series of written answers from junior defence minister Philip Dunne.
He was responding to parliamentary questions tabled by Liberal Democrat MP Mike Hancock, the member for Portsmouth South.
Animal testing was more widespread than Mr Hancock realised
Mr Hancock said he was shocked by the statistics which, until now, were never made generally public.
Last month the British Union for the Abolition of Vivisection highlighted "disturbing and cruel" experiments at Porton Down, said to include live pigs being blasted with explosives and forced to inhale mustard gas, monkeys being infected with anthrax and guinea pigs being killed with nerve agent.
Mr Dunne, the minister responsible for defence science and technology, listed the number of animal procedures undertaken at DSTL Porton Down over the last three years.
The figure has risen from 8,452 in 2009 to 9,582 in 2010 and 9,882 last year, he revealed.
The animals involved were pigs, rabbits, monkeys and rodents.
All scientific experiments on animals, including those at Porton Down, have to be licensed by the Home Office under the proviso that suffering is minimised as much as possible.
Procedures are graded according to the severity of harm or suffering they inflict.
Of the 21 "active" projects at Porton Down, four are "unclassified", three are "mild", six are "moderate" and eight are categorised as "substantial", said Mr Dunne.
A moderate procedure may cause animals a "noticeable degree of pain, suffering, distress or lasting harm", according to the Home Office definition. Substantial severity "may cause a major departure from the animal's usual state of health or well-being with significant or prolonged animal suffering".
Mr Hancock said: "I was shocked to learn that almost 10,000 animal experiments are taking place at Porton Down every year, including ones inflicting substantial levels of suffering.
"The details were not included in the annual statistics published by the Home Office and many people will be totally unaware that this suffering is occurring.
"It is important that the Ministry of Defence routinely gives more information on its use of animals so the public can be fully informed."
In his answers, Mr Dunne stressed that DSTL operates in "strict accordance" with the Animals (Scientific Procedures) Act.
"All the research projects that involve animals are licensed by the Home Office. As part of the licensing process, the researchers have to convince the Home Office that the work is required, that the results cannot be obtained without the use of animals and that every step has been taken to minimise pain and suffering to the animals involved," he said.
BUAV chief executive Michelle Thew said the figures were alarming, describing the experiments as "gruesome." She added: "We need to ensure the safety of soldiers and civilians but the answer does not lay in blowing up or exposing animals to lethal chemical warfare and nerve agents."
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