Failure by both government and industry to deal effectively with disposal of hazardous wastes has left millions of americans exposed to toxic materials, according to a report released yesterday by congressional watchdogs.

The House Commerce subcommittee on oversight and investigation says years of "inadequate disposal practices and the absence of regulation" have left waste disposal sites in such poor cndition that they "now pose an imminent hazard to man and the environment."

The report follows by only one day the announcement by the Environmental Protection Agency that it cannot meet the latest round of congressionally mandated deadlines for promulgating rules covering hazardous waste disposal.

"Our country presently lacks an adequate program to determine where these sites are, to clean up unsafe active and inactive sites, and to provide sufficient facilities for the safe disposal of hazardous wastes in the future," the report concludes.

In a cover letter, subcommittee chairman Bob Eckhardt (D-Tex.) was particularly critical of EPA, which since its creation in 1970 has had authority over hazardous wastes problems.

"EPA has failed to meet statutory deadlines for regulations on disposal of hazardous wastes; has failed to determine the location of all hazardous waste sites; and has not taken vigorous enforcement actions," Rep. Eckhardt said.

Agency officials, defending their actions, said they are bogged down in tedious but necessary detail work, having to respond to every comment they receive on proposed actions, and having to be extremely careful in developing highly technical rules.

In fact the EPA has been burdened in recent years by congressionally mandated cleanups of various segments of the environment.

And because its challenges frequently come from the nation's largest corporations and most prominent law firms, a staffer said, the agency must take special care. "If we procedural, legal or technical errors," he said, "we run a serious risk that our programs will be held up, or remanded in courts."

He said that while the Eckhardt subcommittee is correct in saying that regulations must be promulgated faster, it does not recognize how much time and effort must go into their development.

Eckhardt's letter was also highly critical of industries, which he said have, in many cases, "continued inadequate disposal practices long after they had knowledge that these practices were resulting in water and land contamination."

Congress was asked to share the blame. Eckhardt said it has "allocated far too few funds to deal effectively with a problem of this magnitude."

Moreover, the report states that the 1976 Resource Conservation and Recovery Act (RCRA), the first attempt by Congress to regulate waste disposal, "may have been unrealistic in giving EPA only 18 months to develop national standards for the proper disposal of these wastes."

On Friday, EPA Administrator Douglas M. Costle revealed, in an affidavit filed in U.S. District Court here, that the agency will not be able to meet the latest deadline for developing final RCRA rules. The agency has asked a federal court to waive an earlier mid-1978 deadline set by the act.

Although EPA has taken action in the form of searching for an prosecutting cases of dangerous hazardous waste sites, Costle said, the agency has been unable to develop RCRA rules because it has been bogged down in technicalities.

In a statement accompanying the report, Eckhardt called for a four-part government policy that would place the cost of cleaning up hazardous wastes first on the person responsible. If that is not possible the cost be paid out of general federal revenues. An industry-based fee system should be created to pay when a hazard is created after legislation barring it is passed. Finally, whatever the source of funds used for an immediate cleanup, the government should be able to sue the generator of the wastes to recover cleanup costs.