Six animals rights activists who intimidated companies linked to Huntingdon Life Sciences in an attempt to close down the animal testing lab will hear their sentences today.

Sarah Whitehead, 53, Nicole Vosper, 22, Thomas Harris, 27, Jason Mullan, 32, Nicola Tapping, 29, and Alfie Fitzpatrick, 21, were all members of Stop Huntingdon Animal Cruelty Shac.

Winchester Crown Court has already heard, during the sentencing hearing, the six waged a wide-ranging international conspiracy of intimidation against a host of supply companies to force the closure of Cambridge-based HLS using Shac as a front.

Action included realistic hoax bombs posted to the homes of staff and offices, criminal damage, threats of violence and abusive telephone calls.

Some company directors had leaflets distributed near their home falsely telling neighbours they were convicted paedophiles and others had used tampons sent through the post saying the blood was HIV positive.

Others had words like puppy killer, murderer and scum daubed on their houses, cars or on the roads nearby.

The abuse would only stop when the company issued a capitulation statement on the Shac website and cut links with the lab.

The total cost of damage and increased security costs was £12.6 million, to around 40 companies targeted, the court heard.

The six were part of a larger conspiracy involving the founders members of Shac, Gregg and Natasha Avery and Heather Nicholson, who used the organisation as a front to intimidate companies under badges like the Animal Liberation Front or the Animal Rights Militia.

Whitehead, from Thorncroft Road, Littlehampton, West Sussex, Vosper, from Bay View Terrace, Newquay, Cornwall, and Harris, from Somerville Road, Ringwood, Hampshire, have admitted conspiracy to blackmail companies and suppliers linked to the Cambridge-based company between 2001 and 2008.

Mullan, from Holloway Road, London, Tapping, from Somerville Road, Ringwood and Fitzpatrick, from Knowle Road, Solihull, West Midlands, all pleaded guilty to conspiracy to harm Huntingdon Life Sciences from 2005 to 2008 under the Serious Organised Crime and Police Act 2005 by interfering with companies supplying them.

The maximum jail term for conspiracy to blackmail is 14 years and the conspiracy under the Serious Organised Crime and Police Act 2005 is five years.

Other members of Shac, including the founder members Gregg Avery, Natasha Avery and Nicholson, were jailed in January 2009 at Winchester Crown Court for blackmailing companies linked to HLS.