Oxford University has won an extension of its injunction against activists opposed to the planned animal research laboratory.

Mr Justice Holland's High Court ruling yesterday sees the exclusion zone around the £20m biomedical centre extended along South Parks Road to St Cross Road and further down Mansfield Road.

He rejected a bid to extend the zone to four square miles around the site.

The university has welcomed the ruling, but campaign group Speak described it as a "dismal failure" for the institution.

Protesters will no longer be allowed to use megaphones during their weekly protests outside the lab, but the judge could see no justification for reducing the permitted number of 50 protesters on Thursdays to 12, as requested by the university.

The type of people protected from intimidation and harassment by the injunction has widened to include all contractors who supply goods or services to the university.

Previously staff, students, alumni and contractors working on the biomedical research building were covered.

Protesters will not now be allowed to demonstrate within 100 yards of the home of any protected person, anywhere in the country. They can still organise larger demonstrations in the city, with the approval of police.

The university said an extension of the zone was necessary to protect staff, students and construction workers from harassment.

The judge, who visited the site earlier this month, said the actual or threatened activities of extremists constituted a "serious ongoing problem" for the university.

He said the case should return to court for reconsideration from time to time "in the light of experience and future developments".

University registrar Dr Julie Maxton said the judgement was a significant advance.

She said: "This ruling extends legal protection from such unlawful behaviour to a wider range of people. It also offers a welcome measure of relief to many members of the university who have been subjected to unjustifiable harassment and distress.

"We acknowledge that some individuals and groups are opposed to the building of the university's new biomedical facility and to the potentially life-saving research to be carried out there.

"As a university deeply committed to freedom of speech, we fully recognise the right of such individuals and groups to express their views within the framework of the law. The judgement protects that right, while making it clear that it cannot be used as a cloak for unlawful activity and behaviour."

Robert Cogswell, a spokesman for Speak, said: "There's been a limited extension but we are very happy with the order. We consider their injunction a dismal failure of their legal team. It's going to make very little difference to the injunction they got in 2004.

"Oxford University is presenting this as a victory but if you compare what they asked for with what they got, it tells a different story.

"They obviously have to justify the hundreds of thousands of pounds spent on legal fees.

"The campaign goes on, we're still here and our intention is to stop the lab."