A cancer specialist caught in an "increasing moral dilemma" was jailed for three years yesterday after sabotaging an Oxfordshire firm linked to an animal research laboratory.

Northampton Crown Court heard how Joseph Harris, 26, from Burlesdon in Hampshire, caused £11,400 damage by glueing locks, cutting air conditioning cables and spraying slogans on the walls of Atlas Material Testing Solutions in Granville Way, Bicester.

Among the slogans he wrote were: "This company kills puppies" and "We have found you".

As well as the Bicester firm, the court heard Harris had also attacked companies in Northampton and Nottingham linked to Cambridgeshire's Huntingdon Life Sciences laboratory.

Harris, who had admitted three counts of interfering with business relationships to harm an animal research organisation at a previous hearing, is the first person to be convicted under new legislation targeting animal rights campaigners.

Timothy Palmer, prosecuting, said Harris caused £25,000 damage in total and was caught by police in Northampton on January 15 this year - the same night he attacked the Bicester company.

He said officers found bolt croppers, a hammer, a torch, glue and spray paint in his rucksack - as well as a map of Oxford and animal rights literature - in his car.

Mr Palmer said Atlas, whose contract with Huntingdon was worth just £1,000 a year, had been listed on an animal rights website and had received hate mail from campaigners.

The court heard how Harris, who was working on a treatment for pancreatic cancer after completing his PhD, had come under increasing pressure to conduct animal experiments.

Rebecca Trowler, defending, said Harris had campaigned against animal testing as an undergraduate student.

She said that although he had never tested on animals himself, his work had relied on the findings of colleagues who did.

Ms Trowler said: "This resulted in an increasing moral dilemma and a feeling of guilt.

"His girlfriend with whom he was involved had ended the relationship because of his continued work in the field of medical research because she disapproved. He, in his own words, had come to a breaking point."

Ms Trowler said colleagues had described Harris as an "excellent scientist" with a brilliant career ahead of him - but added he had now lost his job.

Sentencing Harris to three years in prison, Judge Ian Alexander said: "You are a highly intelligent and motivated young man, but you have developed a warped moral justification as an explanation for your serious criminal actions."

Mel Broughton, of the animal rights group Speak, which has been protesting against the building of an Oxford University animal testing lab in the city, said: "I 'm disgusted that he has been sent to prison for three years for damage to property whereas people who are found guilty of harming animals are given community service orders or not even charged."