The prime minister has pledged to redouble efforts to end the criminal activities of animal rights extremists.

Writing in the Sunday Telegraph, Tony Blair slammed the “appalling” activities of anti-vivisection extremists and reiterated his administration’s support for animal testing.

He said his government would consult on plans to keep shareholders’ names secret in a bid to protect medical research.

His comments come after extremists threatened to publish the names of shareholders in GlaxoSmithKline unless they sold their shares. The pharmaceutical firm won an injunction preventing any such move.

And on Thursday, four people were imprisoned for orchestrating a six-year hate campaign against the owners of a guinea pig farm and for robbing a pensioner’s body from her grave.

Mr Blair wrote: “The appalling details of the campaign of intimidation – which include grave robbing – show the depths to which the animal extremists are prepared to stoop.

“We will also consult further on exempting companies from providing full public details of shareholders in future.

“If more measures are needed to protect individuals, universities and firms or to root out the criminal extremist fringe, we will provide them.”

Mr Blair said British scientists and firms were at the cutting edge of medical research and made a “huge contribution to human health and well-being”, adding: “They deserve our thanks, support and protection.”

Mr Blair also said he intended to sign the so-called people’s petition in support of animal testing in Britain.