Hundreds of hazardous waste landfills are operating in violation of federal regulations designed to protect the public from exposure to dangerous chemicals, a congressional group said yesterday.

In a letter to Environmental Protection Agency Administrator William D. Ruckelshaus, seven members of the House Government Operations environment subcommittee contended that the government "is, in essence, sanctioning the operation of thousands of waste facilities throughout the nation which may pose threats to public health and the environment."

The letter was signed by subcommittee Chairman Mike Synar (D-Okla.), ranking minority member Lyle Williams (R-Ohio) and five Democratic subcommittee members.

Citing reports from the EPA's regional offices, the House members said as much as 74 percent of the facilities in some regions are not in compliance with rules that say they must monitor groundwater for contamination. A nationwide sampling by an agency consultant found only 36 percent in total compliance with monitoring requirements.

Such monitoring "is an essential first line of defense against the destruction of this nation's precious underground drinking water supply," which provides water to more than 100 million Americans, the letter said.

The EPA's management of the Resource Conservation and Recovery Act (RCRA), the 1976 law enacted to prevent recurrences of the type of chemical contamination at Love Canal in New York and Times Beach, Mo., that made headlines, has come under increasingly sharp attack in recent months.

Nearly 9,000 hazardous waste disposal sites operate under temporary permits from the EPA, which has yet to approve final permits under the 7-year-old law.

Citizen groups have contended that the engineering requirements for new landfills are inadequate to protect public health, and environmentalists have criticized a provision that allowed landfill operators to close dozens of potentially dangerous sites without taking responsibility for any subsequent contamination.

The House members told Ruckelshaus that the EPA does not have enough inspectors, lawyers or money to handle the job. A report filed by the New York regional office said eight of 15 positions are vacant in the two divisions that handle RCRA, but "the real problem lies in the enforcement division, where only two attorneys are assigned to RCRA."