In a posting on an internet site, the Animal Liberation Front (ALF) has told its supporters that any academic, student or company connected to Oxford is a legitimate target, irrespective of whether they are involved in animal research.

The warning threatens to turn the laboratory into one of the biggest confrontations between animal rights activists and the authorities.

This weekend security sources confirmed that the government was underwriting the multi-million-pound cost of the security operation, one of the most sophisticated mounted by an animal research facility.

Up to 100 security experts, including former soldiers, have been recruited for “counter-surveillance” operations and protection of key workers.

In a sign that the government is determined to take on the activists, it has also emerged that it has earmarked another £20m that can be used for animal research facilities.

Oxford University said last week that it was “appalled” by the ALF statement, but was determined to press ahead with the new laboratory.

The Research Defence Society (RDS) said it was concerned that the threat marked the prospect of a “new era” of violence in the animal rights movement.

The statement, circulated to activists this month, said: “The ALF is calling out to the movement to unite and fight against the university on a maximum impact scale. We must target professors, teachers, heads, students, investors, partners, supporters and anyone that dares to deal in any part of the university.”

Last week every builder working on the new laboratory was masked in a balaclava and accompanied by a personal security guard when walking outside the perimeter. The identity of the contractor has not been disclosed.

One of the most sustained and intimidating campaigns to date by animal rights activists has been against Huntingdon Life Sciences (HLS), a commercial centre for animal experiments in Cambridgeshire.

Brian Cass, chief executive of HLS, was attacked with a baseball bat, another member of staff had ammonia thrown in his face and the company’s investors were threatened. HLS’s listing on the New York Stock Exchange was postponed after threats.

Plans to build an animal primate laboratory in Cambridge were abandoned in early 2004 after a campaign. The decision was a blow to Tony Blair, who had given his personal support to the project.

Oxford University said that 98% of animal experiments in the laboratory would be on rodents and fish.

Animal campaigners say the experiments are unnecessary and cause the animals needless suffering.

In July 2004 Montpellier, the contractor building the Oxford laboratory, pulled out after intimidation.

The Department of Trade and Industry and Oxford University have now agreed a joint response to any threats. Work started again on the laboratory site at the end of last year.

It is understood that in addition to uniformed security guards, a team of former military surveillance officers has been recruited for “counter- surveillance” to ensure that key staff and contractors are not being monitored.

Thames Valley police has also created a special unit to combat extremists. It has been allocated extra Home Office money for the project, called Operation Rumble. An injunction has been issued against animal rights groups and individual activists prohibiting them from threatening staff, intimidating contractors and entering university grounds.

Last July the ALF claimed responsibility for an arson attack on a boat house belonging to Hertford College. It is also claiming responsibility for vandalising the property of an Oxford firm of architects which works for the university.

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