Sen. Bill Nelson, D-Fla., called the inquiry flawed because the office of the inspector general failed to interview one of the main complainants, WFLA-TV, Tampa, reported Monday.
The Energy Employees Occupational Illness Compensation Program passed by Congress in 2000 was supposed to make it easy for sick workers at the General Electric plant in Largo to get help.
But critics, like Nelson, say it turned into a bureaucratic nightmare.
An investigation of the program began after a former claims examiner named Anne Block said on News Channel 8 that she had been instructed to inappropriately deny claims.
The report by the inspector general said it was unable to corroborate Block's charges but Sen. Nelson said they never interviewed her.
"The IG report that just came out did not even interview one of the main complainants," Nelson said.