The study cites six facilities where a major chemical release could kill or injure as many as 1 million people, and another 15 facilities that could each affect 100,000 people.

A toxic release at one plant in northern New Jersey could affect as many as 12 million people, including residents of New York, and one in the South of the state could send a cloud of deadly chlorine gas into Philadelphia, it said.

Elvin Montero, a spokesman for the Chemistry Council of New Jersey, which represents chemical manufacturers, said the study itself undermined security by releasing information about the locations and activities of chemical manufacturers that has not been widely available since the attacks of Sept. 11.

He said the New Jersey chemical industry has spent more than US$100 million on security since the 2001 attacks and is satisfied with security measures.

The group behind the study called upon the administration of New Jersey Gov. Jon Corzine to conduct a thorough assessment of chemical industry vulnerabilities and impose mandatory security standards on the chemical industry rather than relying on the current voluntary guidelines.

The study, which claims to be the first to use data filed by chemical manufacturers with state and federal regulators, argues that additional security is needed to stop chemical plants being used as weapons by terrorists.

"We don't have a cohesive national strategy to protect these potential weapons of mass destruction where it is practical and feasible to do so," said Paul Orum, a consultant on the project.

Anthony Coley, a spokesman for the governor, said the administration accepts that tougher security is needed at the state's chemical plants.