Hiring private contractors to do work for the federal government costs more than having a federal employee do the same work, according to a new study by the Project on Government Oversight. In fact, on average, contractors charge the government twice as much as it pays federal workers.

There has been an ideological push since the 1980s to outsource government work to the private sector. Supporters have justified this by claiming that the private sector will do the work more cheaply, but this argument is divorced from the reality of government contracts.

Private contractors have been ripping the federal government off for decades. For example, in May Boeing had to refund the U.S. Army for massive overcharges — in one case, the company charged almost $1,700 for an $8 spare part.

The Commission on Wartime Contracting also found that private contractors have wasted or lost more than $30 billion in taxpayer money in Iraq and Afghanistan since the wars began. That’s a sixth of the money we have paid them.

The ideological pushers for outsourcing government to the private sector shouldn’t plead ignorance, either. All the way back in 1991, a congressional study found that the government could save money by using its own employees instead of private contractors.

Fiscal hawks who demand cuts in government spending should take careful note of these reports — they are usually the same people who want to cut the federal workforce and sell off government functions to the private sector. Instead of being blinded by ideology, they must engage with the reality of government contracting.