A builder at the lab site in South Parks Road Animal rights groups have issued chilling warnings after work resumed on Oxford University's new animal testing lab yesterday.

Robin Webb, press officer for the Animal Liberation Front, said: "Clearly, with what's happened since the proposals were originally floated, ALF activists will continue their campaign to stop the building of this lab.

"This may even increase their determination. And anything associated with Oxford University will be perceived as a legitimate target."

And last night the animal rights group Speak sent an email to all its members urging them to take action and including a list of the names and contact details of donor companies.

The email, entitled A Call to Action, read: "We took on the might of Oxford University, the pharmaceutical industry and the Government and we defeated them.

"Now we must redouble our efforts in order to defeat them once again and Oxford University can rest assured that Speak will never give up as long as the new animal torture centre stands in South Parks Rd."

Referring to the list of 54 companies, including Microsoft and Vodafone, the email said: "All of them are aware of the horrors being perpetrated against non-human animals inside the walls of the university. Now more than ever these companies need to be contacted and informed of exactly the sort of institution they are helping to fund."

The email ended: "Let the battle begin."

As reported in the final edition of yesterday's Oxford Mail, the £18m complex will replace a number of existing laboratories, and incorporate all animal experiments -- on live monkeys, rodents, amphibians and fish -- under one roof.

It was supposed to be built in two phases, with the first due to open this autumn, but work was suspended in July last year after contractors complained of intimidation.

The Metropolitan Police National Extremism Tactical Coordination Unit was called in after contractors, Montpelier, had paint poured over bosses' cars and received letters warning: "Do business with any part of Oxford University at your peril."

The university won a High Court injunction banning protestors from within 100 yards of the site.

But the ALF merely stepped up its campaign, unsuccessfully attempting to firebomb a sports pavilion owned by Corpus Christi College off Whitehouse Road, South Oxford, in September.

Robert Cogswell, spokesman for Speak, said: "ALF's is an illegal campaign, but whatever they do pales into insignificance when you think about what Oxford University does in its torture labs.

Oxford University registrar, David Holmes, said it was difficult to guess what the activists would do, but he was confident in the continuing protection of the police.

Refusing to reveal which building company had taken over the contract, he added: "The safety of everyone involved is our priority."

Workers at the site yesterday concealed their faces with scarves to hide their identities.