Campaigners and researchers say the measures announced by Jack Straw are unlikely to stop animal rights protestors in their efforts to close the controversial Huntingdon Life Sciences laboratory.

Earlier this week the home secretary vowed to toughen laws to prevent protests outside employees' and directors' homes and the sending of threatening and intimidating mail.

Both sides agree the measures are unlikely to stop protestors who have spent the last two years using a range of measures from picketing banks to sending threatening mail.

A spokesman for People for the Ethical Treatment of Animals told epxNews: "We campaign within the law but we doubt it will stop people who are so appalled by the treatment of animals by the company. Jack Straw's actions will make matters worse because people will be more resentful that the government is siding with a company involved in animal cruelty."

Mark Matfield of the Research Defence Society said: "This has been going on for two years. The tactic has been to slowly wear a company down until they sell shares or drop loans. It's a war of attrition. The home secretary's statement contained nice words but some rather ineffectual, half-baked measures."

"For two years campaigners have been targeting shareholders and the directors of banks. The home secretary should pass laws that make it a criminal offence to organise a campaign of harassment. That way a campaign could be nipped in the bud in six weeks", he said.

Chief executive of the British Union for the Abolition of Vivisection, Michelle Thew, said: "We have campaigned against the Huntingdon laboratory but we do not support violent protest - it is wrong. I am an anti-vivisectionist because I am against violence being carried out; both against people and animals.

"We will be watching very carefully any moves the government makes. They should not stand in the way of peaceful protest. However, I want to make it clear that we do not support the actions that come from the hysteria of animal militancy. The home secretary's announcement gives rise to concern. We are particularly worried about some of the elements in the Freedom of Information Act. This severely restricts open information - without it you cannot have a sensible and reasoned debate," she said.