Senate Health, Education, Labor and Pensions Committee Chairman Tom Harkin, D-IA, said Wednesday that "our government owes it to hardworking Americans to lead by example when it comes to following to our labor laws." MANDEL NGAN/AFP/Getty Images

The federal government awards billions of dollars in contracts each year to companies that routinely violate safety, health and wage regulations, according to a report released Wednesday that calls for stricter measures to hold federal contractors accountable.

The study (pdf) from Democratic leaders on the Senate Health, Education, Labor and Pensions Committee found that nearly 30 percent of companies hit with the highest penalties for federal labor law violations from 2007 to 2012 were also federal contractors.

The report identifies 49 federal contractors that paid $196 million in penalties for nearly 1,800 violations over the six-year period. The same contractors received more than $81 billion in taxpayer dollars in 2012.

In addition, the report says that in 2012, 42 workers died as a result of Occupational Safety and Health Administration (OSHA) violations by federal contractors.

"I fear we are all too often paying companies that fail to pay their workers what they have earned and that regularly subject those workers to unsafe working conditions," said Iowa Sen. Tom Harkin, who chairs the Senate HELP Committee and commissioned the report.

The U.S. government spends over $500 billion each year paying private companies for services ranging from weapons and construction to cleaning and security services. Federal spending for service work alone has tripled since 2000, from $99 billion to $307 billion.

Federal law generally requires government contract officers to assess a company's compliance with federal law before awarding a contract. Federal agencies can also suspend or bar contractors for certain behavior. But the report says government officials often lack the information needed to evaluate violations. A federal database that is supposed to keep track of contractor violations was found to be missing many incidents of misconduct, the report said.