Chemical plants with lax protections from attacks and accidental leaks are being targeted by the Homeland Security Department — before they can be targeted by terrorists.

Homeland Security Secretary Michael Chertoff said Monday his department will crack down on chemical manufacturers and storage facilities that he described as "free riders" — those that haven't beefed up their security measures.

"They're counting on the fact that the industry in general has a good level of investment, and they figure they'll hide among the leaves and essentially freeload on this security work done by others," Chertoff said.

"That's not acceptable," he said. "Progress on this has stalled for too long."

Counterterror experts put the chemical industry at the top of the list of likely terror targets. Congressional investigators have revealed spotty results in how well the chemical industry is prepared to respond in the event of an attack.

At issue is federal regulation of security plans at the nation's 15,000 privately operated chemical plants — one-fifth of which are close to cities and other heavily populated areas.

The chemical industry generally has resisted federal regulation, and large manufacturers have voluntarily taken steps to improve security that they deem adequate. Small chemical firms and plants have largely ignored beefing up safeguards to avoid having to pay for them.

Homeland Security "wants and deserves authority to set federal standards for chemical security, and then enforce those standards," said Chris VandenHeuvel, a spokesman for the American Chemistry Council, which represents large chemical manufacturers. "Four and a half years after 9/11, they still don't have that."

Legislation is pending in the Senate to authorize Homeland Security to shut down facilities that do not comply with minimum safety standards. But the bill by Sens. Susan Collins, R-Maine, and Joseph Lieberman, D-Conn., would largely let the chemical industry draw up its own security plans for the federal government to approve or reject.

Chertoff has not endorsed the plan, but he is expected on Tuesday to outline elements that he said would need to be in acceptable legislation. Congressional staffers said it likely would not encourage facilities to substitute safe substances for hazardous chemicals, as environmentalists have demanded.

Without that provision, "there isn't any security that would be good enough," said Rick Hind of Greenpeace. "A small plane or a high-powered weapon would bypass any gate or fence."