Animal rights activists in the UK could face five years in jail for targeting firms linked to animal research facilities, under new government plans.
Huntingdon Life Sciences has been the focus of activists' protests
The amendment to the Serious Organised Crime and Police Bill covers suppliers such as construction firms or cleaners working for animal research firms.
Measures to stop harassment of animal research facilities and their employees are already in the bill.
Campaigners say the government's proposed laws are not justified.
The amended bill would make it a criminal offence to cause "economic damage" through campaigns of intimidation.
The plans already in the bill include giving police powers to arrest anyone protesting outside the homes of scientists - and the power to ban them from returning to a specified home for three months.
Trade Secretary Patricia Hewitt told BBC News: "We can't have these extremists going way beyond the bounds of peaceful protest into these vicious campaigns of intimidation which have not been stopped by individual laws."
She added: "The simple fact is attacks by animal rights extremists put medical breakthroughs in areas like Aids, cancer and Alzheimer's directly at risk."
Ms Hewitt said the new law would not affect people's "important right" to peaceful protest but would "crack down hard" on extremists committing crimes.
She rejected suggestions by Home Office Minister Hazel Blears that new control orders to put terror suspects under house arrest would apply to animal activists, saying it was a "completely separate issue".
Greg Avery, a spokesman for anti-vivisection pressure group Stop Huntingdon Animal Cruelty, said: "The government is bringing in laws to protect people who murder animals.
"Does this mean that people who are being harassed in other walks of life - such as a woman who is being stalked - are less important?"
The powers to take action against attacks on companies in the supply chain covers company employees, their relatives, business suppliers, plus charity shops and universities.
The government plans follow attacks on centres such as the Huntingdon Life Sciences and a farm in east Staffordshire where guinea pigs are bred for medical research.
Suppliers have also been targeted - last year work on Oxford University's new testing laboratory had to be halted after contractors complained they had been harassed and intimidated by animal rights activists.
Medical Research Council chief executive Professor Colin Blakemore welcomed the announcement, saying: "It is essential that researchers and those working with them are able to carry out their work without fear of intimidation."
For the Conservatives, shadow solicitor general Jonathan Djanogly said: "We have long been calling on the government to protect the industry, which makes a significant contribution to medical research. It is welcome that they have finally seen the importance of this issue."
For the Lib Dems Dr Evan Harris said: "A law to tackle the issue of economic sabotage is clearly required in the field of medical research involving animals.
"But the Liberal Democrats will not support this measure if it applies outside of the area of animal rights extremism where there is a clear problem and where existing laws have proved to be inadequate."