The anti-vivisectionists were detained as hundreds of campaigners arrived for the protest at Hill Grove Farm, Witney, Oxfordshire.

BBC correspondent Simon Jenkins: clampdown is a sign of weariness with campaign (23")

The farm has been the focus of a series of demonstrations over the past year.

Police, who set up road blocks on routes leading to the farm, detained 33 demonstrators as they tried to reach their target. In a demonstration at the farm six weeks ago 24 people were arrested in connection with clashes between police and protesters.

Obstructing police

Among the remaining campaigners arrested, two were held on suspicion of being equipped to steal and three were detained for possession of cannabis.

In an otherwise peaceful protest, two demonstrators were arrested for public order offences and one man was detained for obstructing police. Another protester was arrested on suspicion of theft.

Police put the attendance at 375, while campaigners insisted a figure of 1,000 was more realistic.

Organiser Greg Jennings, of Save the Hill Grove Cats campaign, said: "Animals are being produced here for cruel and unnecessary experiments. We will be coming back until we have seen Hill Grove Farm closed."

Protesters 'behave like mob'

The farm was set up 30 years ago to breed cats for medical research. About 1,000 kittens and their mothers are kept in germ-free conditions before being sold to laboratories.

Owner Christopher Brown declared: "These people want to stop animal experiments yet they behave like a mob.

"They should make reasoned arguments rather than organise demonstrations at huge public cost. Our animals are kept in A1 condition - the protesters have no reason to be here."

A police cordon and reinforced fencing held back the demonstrators from the farmhouse where Mr Brown and his family were sheltering, while a police helicopter hovered overhead.