WASHINGTON — The federal government may be unprepared for future environmental disasters on the scale of the terrorist attacks of September 11, 2001, according to a new report that criticizes the Bush administration’s latest effort to decontaminate apartments near the World Trade Center.

In a study released yesterday, the Government Accountability Office concludes that unless federal agencies develop better plans for handling environmental crises, “the nation may face the same challenges after future disasters” as it did when the collapse of the twin towers blanketed the streets and buildings of Lower Manhattan with toxic dust and debris nearly six years ago.

Studies over the past year have begun to show links between the toxins released during the collapse and respiratory illnesses suffered by people who worked and lived in the area, particularly the rescue workers who toiled for weeks at ground zero.

The GAO report examines a voluntary program that the federal Environmental Protection Agency began in January to test and clean apartments near ground zero following concerns that its initial decontamination attempts were inadequate.

Senator Clinton and two New York lawmakers seized on the findings yesterday to escalate their long-running criticism of the Bush administration’s response to the attacks. At a Capitol Hill press conference yesterday afternoon to release the report, Mrs. Clinton said the study “confirms our worst fears about the Bush administration’s incompetence and indifference” in responding to the health threats posed by the trade center collapse.

“EPA’s first testing and clean-up program was an utter failure, mere window dressing, and today’s GAO report confirms that the second program is no better,” Rep. Jerrold Nadler, whose district includes the trade center site, said.

Mrs. Clinton, along with Mr. Nadler and Rep. Carolyn Maloney, requested the study from the GAO, which is the investigatory arm of Congress.

The Democratic presidential front-runner has assumed a leading role on issues related to the September 11 attacks, in anticipation of a possible general election battle with Mayor Giuliani, whose widely hailed performance in the immediate aftermath of the disaster has helped vault him to the national lead in the Republican primary race.

Mr. Giuliani also has drawn criticism from some corners for the city’s response to the attacks. Asked yesterday whether the city, and the former mayor in particular, bore any responsibility for the environmental and health problems, Mrs. Clinton said she was focusing on the federal response, but she allowed that there were “problems at all levels of government.” She also referenced a public hearing in February 2002, during which she said city officials “readily admitted they were ill-prepared.”

The EPA first launched a program to test and clean more than 4,100 Lower Manhattan apartments in 2002 and 2003, but following recommendations from the agency’s inspector general, it appointed an expert advisory panel to devise plans for a second, expanded decontamination program in 2004.

But the EPA did not follow its own panel’s recommendations, the GAO concluded, which included testing for contaminants other than asbestos, enhancing its methods, and expanding the boundaries of the cleanup to include offices and apartments north of Canal Street and into Brooklyn. That decision “may limit the overall effectiveness of its program,” the GAO report found.

A majority of the EPA committee members told GAO investigators that they “do not believe the panel successfully met any of its goals,” blaming the agency for poor management and accusing officials of refusing to allow the panel to issue a final report.

Just 272 apartment owners and 25 whole buildings have signed up for the current program, and the GAO blames the EPA for discouraging participation by putting out incomplete and misleading information to promote the program.

“EPA has acted upon lessons learned about its preparedness following the [World Trade Center] disaster, but we are uncertain about how completely EPA has laid the groundwork for effective response to indoor contamination following future disasters,” GAO evaluators wrote.

The GAO recommended the agency develop improved guidelines and plans for responding in the future, including better cost estimates and protocols that specifically address indoor contamination.

The EPA challenged the GAO’s findings in a 26-page response to a draft of the report it received in August, various parts of which it characterized as misleading, confusing, and inaccurate.

The response said the EPA is working with other federal agencies on updated response plans for environmental crises.

In a statement yesterday, the EPA’s regional administrator for New York, Alan Steinberg, said that based on the final GAO report, “it appears EPA’s detailed, factual comments were largely ignored.”

The Bloomberg administration declined to comment on the GAO findings yesterday.

For the Democratic lawmakers, and Mrs. Clinton in particular, the report fed into themes of portraying the Bush administration as overly secretive and concerned with political considerations over scientific evidence and public health.

“This is about whether we can trust our government to do what it should to protect us,” Mrs. Clinton said.

A spokeswoman for the EPA, Mary Mears, declined comment on the criticism from Mrs. Clinton, Mr. Nadler, and Mrs. Maloney, saying agency officials were “certainly well aware of their concerns.”