“We have a crisis in wage theft, and the Department of Labor has not been aggressive enough in recent years,” said Kim Bobo, executive director of Interfaith Worker Justice, a group that advocates for low-wage workers. “The new secretary of labor says she’s the new sheriff in town, but I’m concerned she’s facing the wild, wild West of wage theft.”

Secretary of Labor Hilda L. Solis said she took the report’s findings seriously.

“I am committed to ensuring that every worker is paid at least the minimum wage,” Ms. Solis said, “that those who work overtime are properly compensated, that child labor laws are strictly enforced and that every worker is provided a safe and healthful environment.”

Ms. Solis said the Wage and Hour Division planned to increase its staff by a third by hiring 250 investigators  100 of them as part of the federal stimulus package  “to refocus the agency on these enforcement responsibilities” and “ensure that contractors on stimulus projects are in compliance with the applicable laws.”

Ms. Solis said the hirings would “reinvigorate the work of this important agency.”

Ms. Solis’s predecessor, Elaine L. Chao, often defended the Wage and Hour Division, saying it had concentrated on larger, tougher cases, and secured back wages for more than 300,000 workers a year and collected more than twice as much annually as the division had done in the final years of the Clinton administration.

The report concluded that the Wage and Hour Division had mishandled more serious cases 19 percent of the time. In such cases, the accountability office said, the division did not begin an investigation for six months, did not complete an investigation for a year, did not assess back wages when violations were clearly identified and did not refer cases to litigation when warranted.

“When you have weak penalties and weak enforcement, that’s a deadly combination for workers,” said Representative George Miller, Democrat of California, who, as chairman of the House Education and Labor Committee, asked the accountability office to do the report. “It’s clear that under the existing system, employers feel they can steal workers’ wages with impunity, and that has to change.”

Mr. Miller, whose committee is scheduled to hold a hearing on wage and hour enforcement on Wednesday, said he would push to enact tougher penalties for wage violations and laws that made it easier for workers to join class-action lawsuits.