More recently, the White House has been mum on whether it will use this leverage again. But pressure is mounting. Gay-rights advocates have called on the Obama administration to issue an executive order banning discrimination by federal contractors. Environmentalists have said the government could go a long way toward controlling climate change simply by tightening fuel-efficiency requirements on the government’s roughly 600,000-vehicle fleet. This alone would force changes throughout the entire auto market, they say.

Yet most of the discussion in recent months has focused on ways the government can use its buying power to improve wages and working conditions, both domestically and abroad. In response to revelations that many federal agencies rely on garment factories overseas that break local labor laws, several lawmakers said this month that they planned to introduce legislation requiring agencies to reveal which foreign suppliers they used and to submit to third-party audits. And Representative Carolyn Maloney, Democrat of New York, and labor advocates wrote the president this month asking him to issue an executive order on the matter.

The State Department also convened a workshop this month to discuss ways for the federal government to bring its low-bid procurement practices more in line with the administration’s high-road policy objectives on labor and human rights.

In December, a congressional report found that the federal government did a relatively poor job preventing taxpayer money from going to contractors with labor violations. The report, written by the Senate Health, Education, Labor and Pensions Committee, said that tens of billions of dollars in contracts had gone in recent years to companies that were found to have violated federal safety and wage laws and paid millions in penalties. At least 18 federal contractors were among the recipients of the largest 100 penalties issued by the Occupational Safety and Health Administration between 2007 and 2012. The report called on the government to weigh a company’s safety and wage violations more closely as it awarded contracts.