The widow of a senior pharmaceuticals executive has told of the moment her £40,000 BMW was set alight only feet from her home.

Animal rights militants claim to have carried out the attack even though they knew their intended target had been dead for more than a year.

They claimed responsibility on a web site used by fanatics, boasting to the late Alexander Grant his work would "come to haunt you forever even when you have gone".

They claimed to have planted two incendiary devices beneath Kathryn Grant's car although police investigations have not confirmed this was the cause of the fire.

Her husband Alexander was, until his death aged 49 in March last year, managing director of the UK division of pharmaceutical giant Roche, which employs more than 200 staff at its UK headquarters in Lewes.

He had never worked in animal laboratories but his company's links to Huntingdon Life Sciences (HLS), a firm at the centre of a long-running hate campaign, made him a target for animal rights terrorists - even after his death.

Mrs Grant, 51, and her 15-year-old son were in when the family car was destroyed outside their home in Hove.

She assumed a firework must have struck her car accidentally. She told reporters: "As I racked my brains for who might have done it. I remembered a few years ago there was a bit of hassle at Roche with animal rights demonstrators.

"They were obviously not that bothered who was in the house and what could have happened."

Although the attack took place on October 20 it was not until last week when the details were posted anonymously on an anti-vivisection web site used by extremists around the world that the motive behind the attack was confirmed.

The militants boasted: "In October we carried out the operation at Grant's address planting two incendiary devices under an expensive four wheel drive totally destroying it.

"People who sign contracts with or deal with Huntingdon need to realise that your decisions will come back to haunt you forever even when you have gone."

The attack is the latest in a wave of violence against firms with links to HLS, no matter how tenuous.

It follows the firebombing of the house of a senior executive of pharmaceutical firm GlaxoSmith Kline and of a chain of daycare nurseries which provided childcare vouchers for HLS employees.

A group calling itself the Animal Rights Militia claimed responsibility, posting its claims on the same web site linked to a US magazine, Bite Back.

A spokeswoman for Roche, which is planning to move to Burgess Hill next year, said: "We are waiting to have the incident fully investigated by the police. Security is a top priority for the company. That is incorporated in the way we run our operations."

Police were called by the fire service after firefighters attended the house on October 13 at about 9pm.

The spokesman said: "We are treating it as an arson attack so we are treating it seriously."