WASHINGTON — Private security contractors in Afghanistan have used U.S. funds to hire warlords and Taliban conspirators to guard military outposts, endangering U.S. personnel, according to a Senate report released Thursday.

The report by the Senate Armed Services Committee focuses on two companies and alleges they paid hundreds of thousands of dollars to hire local militias. The leader of one such militia was killed during a raid by U.S. forces on a Taliban meeting at his home, according to the report.

“We must shut off the spigot of U.S. dollars going into the pockets of warlords and power brokers who act contrary to our interest and weakens the support of the Afghan people toward their government,” said Sen. Carl Levin, the Democratic chairman of the committee.

The committee’s report, an analysis of 125 contracts provided by the Department of Defense, also lashes out at lax oversight of security contracts. The Defense Department often showed little to no due diligence before awarding millions of dollars to companies and did not follow up on results, an Armed Service committee investigator said.

Afghan President Hamid Karzai said in August that he wanted all private security firms to leave the country by the end of the year. U.S. military and diplomatic officials have called that time line unrealistic.

Republican senators on the committee criticized the report for only focusing on two firms. While there is “real and significant potential for problems associated with the use of private security contractors,” the report “cannot be read as a balanced and comprehensive record of a controversial and difficult issue,” according to a letter signed by Republican committee members.

The report provides details of local Afghans hired by security firms who have fired on American troops, stood guard while high on opium or stacked rocks to mimic a soldier standing his post.

ArmorGroup, a subsidiary of a U.K.-based global security firm, draws the brunt of the criticism for hiring local warlords who later killed each other or were killed by U.S. troops in fighting against the Taliban, the report said.

Internal ArmorGroup documents nicknamed two warlords Mr. Pink and Mr. White after characters in the Quentin Tarantino film “Reservoir Dogs,” the report said. As time passed, Mr. Pink killed Mr. White, then fled the area. He was later replaced by Mr. White I and Mr. White II, the report said.

When ArmorGroup purged several employees because of ties to the Taliban, those same employees signed up for jobs at another security firm, Tennessee-based EOD Technology, the report alleged.

EOD Technology guards bases for U.S. embassies around the world.

Calls to ArmorGroup North America for comment were not returned. In a statement, EOD Technology said it had provided names of its Afghan hires to DOD for review.