Mr. Weil said the nation was in a long-term period during which labor standards and wage compliance have eroded. “It’s unfortunate that we’re finding these violations when the minimum wage is at its lowest level in a long, long time,” after factoring in inflation, he said.

The study said these pay violations ended up costing taxpayers. As a rest of the violations, school breakfast and lunch programs spent an additional $15.6 million in California and $7.8 million in New York in fiscal 2011, the report said. And annual spending on food stamps rose nearly $11 million in California and $33.6 million in New York because of the violations.

In a speech prepared for delivery on Thursday, Tom Perez, the labor secretary, pledges stepped-up enforcement against such violations. “The law is only as effective as the political will of those enforcing,” says the text, which is to be given at a conference on wage enforcement at the Center for American Progress in Washington.

The number of investigators in the Wage and Hour Division has increased to 1,040 from 731 in 2008, the Labor Department said. Since 2009 the department has recovered $1 billion in back wages for workers who suffered minimum-wage and other violations.

Mr. Perez said most employers complied with wage laws, but that bad actors put pressure on others to break the law.

“When we crack down on unscrupulous employers, we send a strong message to similar employers about our vigilance,” his speech text says. “We create ripple effects, as a single investigation can resonate throughout that sector, influencing employer behavior and reforming a race-to-the-bottom culture.”

In recent years, workers have brought a flood of lawsuits accusing their employers of paying them less than the minimum wage and failing to pay overtime. For instance, Guadalupe Salazar, a cashier at a McDonald’s in Oakland, Calif., said her paychecks repeatedly missed a few hours of work time and overtime pay, sometimes bringing her overall pay below the minimum wage. She has joined one of several lawsuits against McDonald’s and several of its franchise operators, asserting that workers were cheated out of overtime, some of their hours were erased from timecards and they had to work off the clock.