Police have alerted Midland education authorities about a teacher who has vowed to return to the classroom despite serving a prison sentence connected with animal rights extremism.
The warning came as John Ablewhite - a supply teacher who is thought to be ringleader of the Save the Newchurch Guinea Pigs group - told supporters he planned to teach children about "animal rights and veganism".
He made his promise as 200 animal liberation campaigners staged a "Victory Party" to celebrate the closing of a Staffordshire farm where guinea pigs were bred for laboratory testing.
Ablewhite, aged 34, is a secondary school teacher from Wolverhampton and is one of the two leaders of a six-year campaign against Darley Oaks Farm in Newchurch.
In 2001 he served nine months in prison for attacking the North Yorkshire home of Leonard Cass, brother of Brian Cass, managing director of Huntingdon Life Sciences. The attack caused £2,000 damage.
He told supporters at Saturday's event: "When I am invited back into the classroom to teach - which I will - I will teach children about animal rights and veganism."
Inspector David Bird, of Staffordshire Police's specialist environmental protest unit, said there was concern about Ablewhite's extremist background and the unit had contacted potential employers in the area.
"We've all got strong views on one thing or another but he has been convicted of a criminal offence," he said.
David Cameron, Conservative education spokesman, called on the General Teaching Council to look at Ablewhite's case.
It has powers to apply sanctions against teachers - even prohibiting them from teaching if a person on its register is found to have a relevant criminal conviction.
Conservative MP for Lichfield, Michael Fabricant, said he hoped LEAs would use their "good sense" and refuse to employ individuals who hold extreme views.
Last year Mr Ablewhite was arrested and released without charge by Staffordshire Police in connection with the desecration of the grave of Gladys Hammond. Mrs Hammond, aged 82, was the mother-in-law of Chris Hall, whose family runs Darley Oaks farm. Despite massive police searches Mrs Hammond's remains have never been recovered.
On Saturday the protesters who gathered to celebrate the farm's closure denied all knowledge of the graverobbing and some suggested the crime was an attempt to discredit the movement.
Mel Broughton, a member of the Speak campaign group, told the crowd: "I will never, ever, condemn those who take direct action for the violence committed against millions of animals around the world."
On the same day the Venerable Bob Jackson, Archdeacon of Walsall, made a new public appeal for the people responsible for taking Mrs Hammond's remains to show "compassion and decency".