Prime Minister Tony Blair yesterday declared his support for animal testing and attacked protesters trying to stop the building of a controversial Oxford University laboratory.

Mr Blair announced he was taking the unusual step of signing a petition supporting animal testing, which has been launched by the Coalition for Medical Progress, as he said the Government would move against the "extremist fringe" of the protest movement.

Trying to rally support, he said: "(It) is a sign of just how important I believe it is that as many people as possible stand up against the tiny group of extremists threatening medical research and advances in this country."

But campaigners against the construction of the £18m animal testing laboratory in South Parks Road said they would not be distracted by the Premier's intervention.

Mr Blair revealed the Government was to consult on plans to keep shareholders' names secret, to protect the scientists and companies which had saved hundreds of millions of lives.

The proposal comes after extremists threatened shareholders in drugs company GlaxoSmithKline they would have their names published on the Internet unless they sold their shares.

Mr Blair added: "If more measures are needed to protect individuals, universities and firms or to root out the criminal extremist fringe, we will provide them."

Animal rights extremists have delayed the completion of the Oxford laboratory, after the contractor pulled out citing security concerns. Work restarted at the end of last year, following a 16-month delay.

Mel Broughton, a spokesman for Speak, which is campaigning against the construction of the laboratory, said: "This is simply grandstanding by Blair to deflect from his own troubles.

"It's a sop to the pharmaceutical industry and it certainly won't affect in any way what we're trying to achieve."

A movement backing the building of the lab has been launched this year, with a second rally in the city planned next month.

Oxford West and Abingdon MP Dr Evan Harris, who supports the lab, said: "Mr Blair needs to do more than sign petitions. He needs to sign cheques that will ensure that the police and the intelligence services have the resources to break open the extremist movement."

Laurie Pycroft, spokesman for the group Pro-Test, which is in favour of animal testing, was not available for comment.

The University of Oxford returns to the High Court on Thursday seeking an extended injunction further curbing the protests.