MI5 is poised to help to fight animal rights extremists amid growing fears that their intimidation is undermining key British industries.

Senior officers from the Security Service are consulting the Home Office about the need for intelligence-gathering to counter the threat to pharmaceutical companies.

The development comes after revelations in The Times yesterday that two of the world’s biggest drug manufacturers have threatened to withdraw new research investment from Britain unless action is taken.

One, GlaxoSmithKline, invests more than £1 billion a year in Britain. As well as safeguarding national security, MI5 is responsible for protecting “economic wellbeing”.

Its entry into the war against the extremists would prepare for a campaign of infiltration and surveillance.

The Times has learnt that a senior City figure approached to head a campaign to advise and support companies threatened by animal rights extremists refused because he had himself recently been targeted.

The businessman, whom The Times has agreed not to name, said: “My house has been attacked and my family has been threatened on several occasions, so I didn’t want to become involved.”

He said that he was targeted because he had been chairman of a company which did business with Huntingdon Life Sciences, the research company regularly attacked by militants.

The impetus for the campaign came from the National Association of Pension Funds, whose members manage hundreds of billions of pounds on behalf of pension fund members. Other City bodies involved in the talks included the Corporation of London and the Investment Management Association.

If MI5 joins the fight against the extremists, it will be the first time for years that it has switched resources to countering domestic subversion. It scrapped operations against suspected subversive elements some years ago because they were no longer seen as a threat.

Animal welfare extremism has been left to the police as a public order matter and MI5 had previously decided against investigating the most extreme groups.

However, Whitehall sources said that with the increasing number of violent threats against drug companies and research institutions, MI5 could be brought in. “This is now a hot issue,” one Whitehall source said.

The sources said that a final decision would depend on whether the extremists were judged to have crossed into a more dangerous arena.

Police have been trying to combat animal liberation groups since their emergence in the 1970s. One of the problems has been the proliferation of groups and their tight cell structure, modelled on groups such as the IRA.

When demonstrations have been mounted in recent years, organisers have kept the targets secret until supporters arrived at rallying points.

Police sources said that activists had also learnt how to counter the law. When new legislation allowed police to require protesters to remove masks to be filmed, they began to paint their faces as animals instead.

Scotland Yard has led the drive against the extremists for more than 20 years, setting up the Animal Rights National Index, run by a small number of Special Branch officers. But operations against the IRA took precedence.

For many years, the extremists’ tactics mainly involved low-level arson but they have grown more aggresive since the 1990s, with a number of bomb attacks and spreading intimidation.

Individual forces carried out investigations, and there have been notable successes, with one leading figure in the Animal Liberation Front receiving a ten-year sentence for conspiracy to incite others to commit criminal damage. However, there has also been a lack of co-ordination and problems with prosecuting offences such as trespass.

Under pressure from ministers and companies, police forces have now united in operations against rolling demonstrations, which stretch across a number of counties. The National Crime Squad is targeting suspects identified by intelligence operations.

If MI5 becomes involved, the agency would work with the new National Extremism Tactical Co-ordination Unit, formed by chief constables this year and based at Cambridgeshire Police headquarters, which has been policing the demonstrations against Huntingdon Life Sciences and the threats against Cambridge University’s now abandoned plan for a primate laboratory.

Anton Setchell, an assistant chief constable in the Thames Valley force, has become the National Co-ordinator for Domestic Extremism.

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