A report by North Yorkshire's chief constable has failed to explain why the force spent over £500,000 on company cars for senior officers, an MP claims.
There are concerns that some of the force's cars are under-used
The police authority asked Della Cannings to reply to concerns that some of the cars do very little police work.
Her report says the 20-strong fleet of Land Rover Discoveries and Volvo V-70s is "essential" and "value for money".
But Harrogate and Knaresborough MP Phil Willis (LibDem) says some are used so little they do not benefit taxpayers.
The report is due to be considered by the North Yorkshire Police Authority on 7 March.
In her report, Ms Cannings says the provision of vehicles to superintendents and chief superintendents was to "enable them to respond rapidly to the force's operational requirements".
She stressed that the 4x4 vehicles were needed by a police force covering about 3,200 square miles of largely rural land.
Although equipped with flashing blue lights, sirens and satellite navigation systems, they are also available for the officers' private use.
Figures for December 2004 showed that the average monthly business mileage recorded by the so-called "command platform vehicles" was 1,037 miles.
Mr Willis said: "The report does not answer a number of fundamental questions."
He said it gave no details of how many incidents the vehicles had responded to and did not identify how many had done less than the average mileage.
"I know that one car did less than 2,000 miles in more than six months," said Mr Willis.
"The cost benefit of that to the taxpayer of North Yorkshire is nil.
"I readily accept that some of these cars are needed for officers to perform their duties, but do we need a fleet of 20 vehicles costing more than £500,000 when some spend most of their time parked at home or even in the south of France?"