PHOENIX -- An internal audit has determined that the Maricopa County Sheriff's Office violated the county's procurement procedures by agreeing to purchase a $465,000 bus to transport inmates.

The custom-made bus was purchased in October 2008 with the sheriff's jail-enhancement funds, a revenue stream built from fines, penalties and forfeitures, but it has sat idle ever since it was delivered in May because of ongoing disputes between Sheriff Joe Arpaio and county administrators.

In an August news release, Arpaio claimed county management was withholding authorization of the bus as retribution for his investigations into county elected officials and administrators.

“This bus was purchased with money from the Jail Enhancement Fund, not from the county budget,” he said. “As Sheriff, I have sole discretion on how this particular fund is used. We determined this vehicle was critical to enhance our jail operations. It’s time the board and its county manager, David Smith, put public safety above their own political agendas and egos and stop interfering with my mandated duties.”

County officials have said the sheriff's decision to purchase the vehicle was an intentional effort to work around a county freeze on capital purchases.

The audit concludes that the Sheriff's Office circumvented county policies, did not ensure the purchase price was from the lowest bidder and that the sheriff's process did not include controls to protect public funds.