(CNN) - A British contractor working for the US military in Afghanistan charged the government for seven luxury cars -- including Porsches, a Bentley and an Aston Martin -- and billed more than $50 million in questionable costs, according to the summary of a Pentagon audit.
The audit from the Defense Contract Audit Agency, a summary of which was released by Sen. Claire McCaskill on Wednesday, found that New Century Consulting racked up costs that included the luxury vehicles, $42,000 for automatic weapons and salaries of $420,000 to the significant others of the company CEO and CFO as executive assistants.
Sen. Claire McCaskill detailed the findings of the audit in a letter sent this week to Defense Secretary James Mattis. The Missouri Democrat wrote to Mattis asking who was in charge of authorizing the Afghanistan contract and why the contract continued after issues arose.
"Despite all of the listed issues with NCC's performance and billing practices, the Army continued to engage in contracting with NCC for sensitive work in Afghanistan," McCaskill wrote.
New Century Contracting CEO Michael Grunberg said in an email to CNN: "It would be inappropriate for us to comment on an ongoing matter." He told The Associated Press that it "is most unfair and is significantly inaccurate" to say that the executive assistants were paid inappropriate salaries.
Grunberg told the AP that the audit "questioned solely the use and depreciation treatment of vehicles" and that New Century Consulting "accounted for no more than three vehicles across the entire business at any one time."
The Defense Contract Audit Agency did not respond to a request for comment.
McCaskill said the audit was conducted after she and Ohio Republican Sen. Rob Portman expressed concerns over the New Century Consulting contract, which was to provide mentoring and training for the Afghan National Security Forces. The Special Inspector General for Afghanistan Reconstruction in 2015 also raised issues with the contract.
The highlighting of issues over contractor spending comes as the Trump administration is trying to decide a path forward for the US war in Afghanistan. One of the options that has been floated comes from Erik Prince, the controversial former head of the now disbanded Blackwater company, to use supply contractors for a variety of unspecified missions in Afghanistan.
The audit of New Century Consulting focused on costs billed from 2008 through 2013, according to McCaskill's letter, when NCC was a subcontractor to Imperatis, formerly Jorge Scientific --- which faced its own scrutiny in 2012 over conduct in Afghanistan.
The audit found that the seven luxury cars billed included Porsches, Alfa Romeos, a Bentley, an Aston Martin and a Land Rover, according to McCaskill.
"NCC claimed that the vehicles were available to all employees but the vehicles actually were used exclusively by the chief executive officer, chief operating officer, chief financial officer and the significant others of the CEO and CFO," McCaskill wrote.
In addition to the vehicles and automatic weapons, McCaskill said the questionable costs included alcohol, rent, unnecessary licensing fees and personal air travel. She said the DCAA questioned the costs for several reasons, including the lack of a detailed record of the costs or documentation to justify the expenses.
McCaskill wrote that the DCAA is now auditing costs from 2013 to 2016, when New Century Consulting was named the prime contractor for the Afghan contract.