A Freedom Of Information request revealed that, in 2012/13, the force spent £583,733 on hire vehicles.
A spokeswoman for the force said: “Norfolk is a rural county and with many departments now collaborated with Suffolk Constabulary, it is important that officers and staff have vehicles available to carry out their roles.
“Whilst response vehicles are purchased, unmarked vehicles for general transport are often hired which provides flexibility and short-term cover when vehicles are damaged or faulty.