U.S. taxpayers spent $150 million building fancy, hotel-like "villas" staffed with private security for government employees working in Afghanistan rather than having them live on U.S. military bases at a fraction of the cost, according to the top government watchdog charged with monitoring wartime waste.

The lead oversight team auditing U.S. spending in Afghanistan said Thursday the Pentagon's Task Force for Stability and Business Operations spent 20 percent of its budget on private housing and security guards for a "handful" of employees who could have lived on U.S. military bases for little or no extra charge.

"We are concerned that this may be another example of U.S. government officials not looking out for American taxpayers' dollars." — John F. Sopko, Special Inspector General for Afghanistan Reconstruction

"We are concerned that this may be another example of U.S. government officials not looking out for American taxpayers' dollars," John Sopko, special inspector general for Afghanistan reconstruction (SIGAR), told FoxNews.com.

The Department of Defense employees worked for the now-defunct Task Force for Stability and Business Operations, known as TFBSO or the Task Force -- the DOD's premiere program to kick-start the Afghan economy. The $150 million spent on the villas and private security supported "only a handful" and "no more than 5 to 10" TFBSO staff members the majority of the time, according to Sopko.

In a Nov. 25 letter to Defense Secretary Ashton Carter, Sopko requested information on the Task Force's decision to spend nearly a fifth of its budget on the villas and security. From 2010 through 2014, Congress appropriated approximately $822 million to TFBSO for Afghanistan, of which the Task Force spent approximately $766 million.

"SIGAR's preliminary review indicates that TFBSO leadership rented specially furnished, privately owned 'villas' and hired contractors to provide 24-hour building security, food services, and bodyguards for TFBSO staff and visitors traveling in the country," Sopko wrote. "If TFBSO employees had instead lived at DOD facilities in Afghanistan, where housing, security, and food service are routinely provided at little or no extra charge to DOD organizations, it appears the taxpayers would have saved tens of millions of dollars."

Sopko's latest inquiry comes as part of a broader investigation into allegations of financial misuse and criminal activity within the Task Force, which ended in March 2015. In a report published last month, SIGAR found the DOD spent $43 million to build a gas station in Afghanistan that should have cost roughly $500,000.

According to SIGAR, each room at the villas was equipped with luxuries, including a flat screen TV, a DVD player and mini refrigerator. An "investor villa" with "upgraded furniture" and "western-style hotel accommodations" was also provided to TFBSO personnel, SIGAR noted.

While SIGAR said it could not determine what it would have cost for TFBSO employees to live at the U.S. Embassy, it estimated that for 2014 a staff of 10 would have paid roughly $1.8 million to live there.

Sopko said the decision to build the costly villas appears to have been made by Paul Brinkley, former Deputy Under Secretary of Defense and the Task Force's first director. Sopko said Brinkley has not cooperated with his office's request for information.

Brinkley, who now runs a private Dubai-based business development firm, disputed Sopko's claim, saying in an e-mail to FoxNews.com, "I have not been contacted by the Special Inspector General for Afghanistan Reconstruction regarding the questions raised in the letter to the Department of Defense since I departed government service almost five years ago, but would be happy to meet and discuss these topics."

"The Task Force for Business and Stability Operations operated under the authority and oversight of the Secretary of Defense and ISAF command during my tenure," said Brinkley, who left TFBSO in June 2011. "Its unique operating posture -- operating outside of military or diplomatic installations -- was elemental to its successes and was clearly sanctioned by Pentagon leadership as well as the Congress, and covered in a variety of media reports, GAO assessments, and think-tank studies."

"When I ran the task force, we had one mission: help bring normalcy to Afghanistan by encouraging sustained economic growth and employment for the Afghan people and the creation of an Afghan middle class,"he said. "Everything we did was focused on that goal, which is critical to Afghanistan’s ability to someday finance its own security and development needs without US taxpayer support."

Department of Defense spokesman, Army Lt. Col. Joe Sowers, acknowledged receipt of Sopko's Nov. 25 letter to Carter but he declined to comment further about the matter.

"We have received the recent letter from SIGAR and will respond," Sowers told FoxNews.com.

The TFBSO was originally created by the DOD to revitalize Iraq's economy after the U.S.-led invasion in 2003. The program was redirected to Afghanistan in 2009 to lead projects supporting economic development.

A former TFBSO official, speaking on background, said many of the locations where Task Force employees worked in Afghanistan lacked any U.S. military of civilian installations.

"Where appropriate or necessary we did operate on military installations, including Camp Leatherneck in Helmand Province and at Kandahar Air Field," the former official told FoxNews.com. "Our operational construct was approved by the entire chain of command, from the secretary of defense to the combatant commander."

In an interview last month, Sopko told FoxNews.com his office has received "numerous allegations" of criminal activity by the Task Force from former employees as well as "current and former uniformed officers who worked over there, other agencies and contractors." He declined to elaborate on the specifics of the accusations.

A former TFBSO employee, who spoke to FoxNews.com on condition of anonymity, described the villas as hangouts for senior DOD officials who traveled to Afghanistan, "simply to accumulate flying miles."

"They just came in and didn’t do anything but hang out in the villa," the source said.

Cristina Corbin is a reporter for FoxNews.com. Follow her on Twitter @CristinaCorbin.