An animal rights activist has been jailed for six years for her role in a campaign group that targeted a research company with explosive devices, bomb threats, false paedophile accusations and sanitary towels allegedly infected with HIV.

Debbie Vincent, of Pampisford Road, Purley, was convicted in March of conspiracy to blackmail businesses the group suspected had involvement with controversial Huntingdon Life Sciences (HLS).

The 52-year-old, along with other members of Stop Huntington Animal Cruelty (Shac), waged a ten-year campaign of "animal rights extremism" against the Cambridge-based international research company with the aim of forcing its animal testing laboratory to shut.

The sustained campaign of harassment and intimidation saw activists falsely allege the directors of companies that supplied HLS were paedophiles in leaflets distributed to their neighbours, while other directors received used tampons with message claiming they were infected with the Aids virus.

Police said the tactis "went far beyond lawful campaigning".

Detectives believe Shac was also responsible for delivering incendiary devices and violent threats, blocking email and telephone systems and criminal damage, including graffiti on the homes and cars of bosses.

The group would then approach the companies - all based overseas - warning they would continue to be targeted unless they provided a written statement that they had severed all ties with HLS.

Winchester Crown Court heard Vincent joined the campaign in November 2011 and became more heavily involved after its masterminds, Greg and Natasha Avery, were jailed for nine years for blackmail in 2009.

Prosecutor Alastair Nisbet said: "The prosecution did not allege that Debbie Vincent herself had committed any of the direct action offences, but the jury has found her guilty of knowingly being involved in an agreement with others to pursue the objective of Shac by such threatening and intimidating actions."

Vincent was arrested on July 6, 2012 during a lengthy police investigation involving forces across Europe.

Commander Duncan Ball, head of the Met Police's Counter-terrorism team, said: "The court has found that Debbie Vincent's actions in attempting to prevent these companies from going about their legitimate business were a clear breach of the law.

"The tactics used were extremely damaging to those targeted and went far beyond lawful campaigning .

"The MPS remains committed to upholding the right to lawful protest.

However we will not hesitate to pursue and prosecute those who are intent on committing criminal activity of this nature."