Police are to be given new powers to arrest animal rights extremists who protest outside scientists' homes, the Government confirmed today.
The crackdown will also give officers the power to ban protesters from the vicinity of someone's home for three months.
Harassment laws will be strengthened to deal with campaigns aimed at a groups of people working for the same company, such as an animal research laboratory.
At present, the courts have only applied harassment laws to campaigns which have targeted individuals.
Home Office minister Caroline Flint said: "By toughening up the law on protests and harassment, and with robust enforcement by the police, and courts, the Government intends to put a stop to the animal extremists' reign of terror.
"It is wholly unacceptable that a small number of criminal extremists attempt to stop individuals and companies going about their legitimate business."
She added: "The Home Office has already provided the police with tough powers to counter animal extremists and these powers are already being used to good effect, but more needs to be done.
"People have the right to campaign lawfully and peacefully against the use of animals in scientific research.
"But they do not have the right to intimidate people and their families in their own homes, nor do they have the right to harass people at work or destroy their livelihoods."
The new moves will make it an offence for a person to be "outside a home for the purpose of representing to or persuading the resident, or anyone else, that he should not do something he is entitled to do, or that he should do something he is not obliged to do, and causing harassment, alarm or distress to the resident".
The 1997 Protection from Harassment Act will be extended to cover harassment of two or more people who are connected, such as employees of the same company.
It will apply even if each individual is harassed on only one occasion, a Home Office spokesman said.
The detailed proposals were set in out a joint Home Office–Department for Trade and Industry paper entitled Animal Welfare: Human Rights – Protecting People from Animal Rights Extremists.
Trade and Industry Secretary Patricia Hewitt said: "I am proud of the advances in medical research that have been brought about by the work of UK scientists and businesses who make a huge contribution to our economy and prosperity.
"Our lifespan would be shorter, our health worse and our environment and country poorer without these people who carry it out.
"Animal rights extremists do not have the right to harass and physically attack those involved in lawful business and research."