Sen. Maria Cantwell, a Democrat, said the measure would address loopholes and lax enforcement that allow companies to shirk their cleanup responsibilities, forcing taxpayers to pick up the tab.

"We need to make sure it´s the polluter who pays and not the taxpayers," Cantwell said when she introduced the bill April 11. "My legislation will fix environmental laws and empower federal regulators to hold companies accountable."

Cantwell based her bill on the findings of an August 2005 report by the Government Accountability Office, an investigative arm of Congress. The report concluded that corporate polluters were using bankruptcy laws to evade environmental responsibilities, and that the Environmental Protection Agency could do a better job of ensuring that liable parties meet their cleanup obligations.

The existing law allows a parent company to avoid responsibility for environmental cleanups by acting through subsidiaries, Cantwell said. Her bill would direct the EPA to more closely examine the relationship between parent companies and subsidiaries.