WASHINGTON (AP) -- The military's program to inoculate all 2.4 million troops against anthrax as protection against biological warfare is based on ``dangerously narrow scientific'' evidence and should be suspended, a House panel says.

The anthrax vaccine should be considered experimental because its effectiveness against biological warfare is uncertain and the safety of troops taking the anthrax shots is not being monitored adequately, according to the sharply critical report being released Thursday by the Government Reform Committee's national security subcommittee.

A draft of the report obtained by The Associated Press says the immunization program ``is an unmanageably broad military undertaking built on a dangerously narrow scientific and medical foundation.''

Defense spokesman Jim Turner said Wednesday that the department is reviewing the congressional study. Defense officials have said repeatedly the vaccine is safe and effective.

The 80-page report was written by the subcommittee's Republican majority after six hearings on the vaccination program.

The vaccine has come under increasing scrutiny from congressional lawmakers as soldiers, including pilots in the National Guard and reserves, have expressed concerns about taking the six-shot regimen.

Complaints included fevers, muscle pain and dizziness. Some reserve pilots testified they would resign to protect their health and flying careers while other soldiers in the active military have faced courts martial.

In 1998, Defense Secretary William Cohen ordered all active duty and reserve troops to get shots of the anthrax vaccine, starting with soldiers most likely to encounter biological warfare overseas. Some 340,000 service members have been immunized so far.

About 200 to 300 have refused to take it because of concerns about its safety and efficacy, Pentagon officials say.

``We feel the program is a vital force protection program against a known threat,'' Turner said.

Anthrax has never been used in combat, but the Pentagon fears Iraq, North Korea and other countries -- or terrorist groups -- might try. Anthrax is a naturally occurring bacteria found in domesticated animals; it can be produced as dry spores that, when inhaled, cause death within a few days.

The vaccine had been studied mostly for its effectiveness in protecting veterinarians and mill and livestock handlers decades ago against infection from touching animals or animal parts of goats, sheep or cattle.

There is little research concerning the inhalation of anthrax spores by humans and no long-term research on the vaccine, the report says; therefore, the vaccine should be regarded as an investigational drug, requiring the approval of troops to be administered.

The report also says the program should be suspended because some troops have told lawmakers they do not trust medical information provided by the Defense Department and that is hurting troop retention and morale.

The department has engaged in ``absolutist declarations'' and ``heavy-handed propaganda,'' labeling critics as paranoid rather than answering their questions, the report said. Instead of encouraging reporting of adverse reactions, the lawmakers said, the military may have under-reported problems with shots due to an ``institutional culture that is hostile, even resistant, to reports.''