Some medical devices for sensitive uses, from certain hip joints to a type of defibrillator, have won government approval without a close scientific review, congressional investigators said Thursday.

Although Congress ordered the Food and Drug Administration years ago to resolve the issue, the agency approved 228 medical devices without a full scale review from 2003-2007, the Government Accountability Office said in a report.

Some devices approved under the less rigorous process have been recalled because of malfunctions and other problems, according to the consumer group Public Citizen. One device was an external defibrillator to assist heart attack victims.

The report comes as the FDA's Center for Devices and Radiological Health is the subject of allegations that scientists were pressured to approve medical machinery against their professional judgment. Nine FDA scientists wrote the Obama transition team last week complaining that a "corrupted" review process is putting public health at risk.

The allegations are a separate matter from the concerns raised in Thursday's report. But taken together, they probably will raise the level of congressional scrutiny over the FDA's medical devices branch.

"GAO's investigation confirms my concerns that the approval process for medical devices is woefully inadequate," said Rep. Frank Pallone, who heads the House Energy and Commerce Committee's health panel. "For years, Congress has required high-risk medical devices to undergo stringent premarket review, but GAO's findings show that is simply not happening in every case."

Pallone, D-N.J., said he intends to hold hearings on the FDA's oversight of medical devices. The GAO did not look into whether any patients were harmed as a result of devices that got less government scrutiny.

The root of the problem seems to be that the FDA never fully carried out the intent of a decades-old change in the law.

Medical devices include everything from tongue depressors to silicone breast implants and pacemakers. In 1976, Congress set up a three-tiered classification system for devices.

Manufacturers of low-risk devices such as bandages and reading glasses could get cleared by notifying the FDA before going to market. High-risk devices such as pacemakers and heart valves would have to go through tighter scrutiny, and their manufacturers were required to provide evidence of safety and effectiveness. Devices classified as high-risk tended to be ones that are implanted in the body or could spell the difference between life and death.

An exception was carved out for new versions of high-risk devices already on the market.

Manufacturers could get approval by convincing the FDA that these devices were "substantially equivalent" to their precursors. In 1990, Congress ordered the FDA to end the practice, but it has continued even as generations of technology have come and gone.

The report urged the FDA to promptly resolve the problem, either by carrying out full reviews or reclassifying some devices as lower risk, if appropriate.

The FDA acknowledged the problem, but has not set a timetable for resolving it. "In general, we agree with the conclusions and recommendations," said spokeswoman Karen Riley. "We are considering legal and procedural options to accomplish this objective."

The GAO report found that two-dozen distinct types of devices approved without close scrutiny, including metal hip joints, external defibrillators, and electrodes for pacemakers.

"It all adds up to less-than-rigorous device review, and it's placing tens of thousands of Americans at risk," said Peter Lurie, deputy director of Public Citizen's health research group.