An increasing number of animal rights' activists are conducting arson attacks against Oxford University because an injunction has limited their legal right to protest.

That is the view of leading campaigner Robert Cogswell, a spokesman for the Speak organisation, which is campaigning against the new £18m animal laboratory in South Parks Road.

He spoke out after it emerged yesterday that activists from the Animal Liberation Front tried to firebomb a sports pavilion owned by Corpus Christi College off Whitehouse Road, south Oxford, on Saturday.

As reported in the final edition of yesterday's Oxford Mail, police were called by university security staff who discovered that an incendiary device had been planted.

The device was disabled before damage could be caused and firefighters were not required at the scene.

Mr Cogswell said: "We do not condone the ALF's actions but we do not condemn them either.

"The university successfully applied for an injunction to limit our peaceful protests and the more people's rights to protest legally are restricted, the more they could be forced down an illegal route."

The High Court injunction granted in November 2004 prevents protesters from entering a 35-metre no-harassment zone around the building site on South Parks Road.

In July, an arson attack by the ALF caused major damage to the Hertford College boathouse on the Thames, near Donnington Bridge Road.

Following the attempted arson at the weekend, the ALF warned the university that it would "destroy every bit of property you own... to stop you inflicting your profit-driven cruelties on defenceless creatures".

A spokesman for Oxford University said: "The intimidating nature of this message is totally unacceptable."

Following the latest attack, an ALF statement said a group calling themselves the Oxford Arson Squad was responsible.

A spokesman for Oxford police said they were investigating the incident.