The Food and Drug Administration's new chief promised Thursday to crack down on food and drug companies that break the law, as the agency tries to regain its footing after a string of high-profile safety problems.

FDA Commissioner Margaret Hamburg said her agency must act more swiftly and aggressively against companies that don't meet safety standards.

In recent years, the agency's efforts "have been hampered by unreasonable delays" that allowed safety violations to go unaddressed, Hamburg told an audience of food and drug industry lawyers.

'Serious violations have gone unaddressed for far too long.'—FDA Commissioner Margaret Hamburg

The FDA has struggled for years to keep up with its rising responsibilities to oversee health care and food products. Since early 2008, the agency has been criticized for its handling of tainted peanut butter that sickened hundreds, contaminated blood thinners imported from China linked to deaths, and an investigation into a salmonella outbreak that dragged on for weeks before peppers were identified as the culprit.

President Barack Obama tapped Hamburg, a former New York City health commissioner, to try to restore the agency's credibility.

Hamburg emphasized the FDA's responsibility as a regulator.

"The agency must show industry and consumers that we are on the job," Hamburg said. "Companies must have a realistic expectation that if they are crossing the line, they will be caught."

The FDA was seen as drifting during the Bush administration, going long periods without a permanent commissioner who could be an advocate before Congress. Lawmakers piled new responsibilities on the agency, often without the funds to carry them out.

Renewed focus on enforcement

When FDA officials did speak publicly about their work, they often emphasized the agency's role in collaborating with drug makers to bring new therapies to market.

Hamburg acknowledged Thursday that FDA's regulatory actions against companies declined steeply in recent years — a trend documented by the General Accountability Office.

"In some cases, serious violations have gone unaddressed for far too long," she said.

Since Hamburg's confirmation in May, the FDA has taken a series of rapid-fire enforcement actions against companies selling bogus or dangerous products.

In May the agency ordered dozens of websites to stop marketing more than 100 phony swine flu remedies. A month later, regulators warned consumers to stop using the popular nasal decongestant Zicam Cold because it can permanently damage the sense of smell.

Last week the agency sent letters to manufacturers of dietary supplements that actually contain metabolic steroids.

While such actions mark a break from FDA's recent past, Hamburg suggested they will become routine in the months and years ahead.

"I hope that in the future, effective FDA enforcement will not be surprising or out of the ordinary," Hamburg told attendees of the Food and Drug Law Institute conference.