Essex Police air robot lies unused for three years
Essex Police said an unmanned aircraft it bought three years ago for aerial surveillance has never been used because it has not been licensed.
The force said the remote control helicopter was bought in May 2008 at a cost of £22,000.
It had intended to use it to monitor large events and track criminals.
The Civil Aviation Authority (CAA) said Merseyside and Staffordshire had licensed drones but Essex had not applied for permission for its craft.
A CAA spokesman said: "We've had no communication with Essex Police.
"The police can be exempt from a certain number of rules governing the use of unmanned aircraft provided they can show they are able to use them safely."
Police said in a statement: "Essex Police own an air robot which, to date, has not been deployed operationally whilst clarification was obtained regarding licensing legislation.
"It was purchased for crowd safety at events such as the V Festival and crime prevention."
The force said it had been intending to sell the drone but the sale was not going ahead because of "difficulty contacting the proposed purchaser".
The CAA said it needed to be consulted over any use of the drones, that can fly up to 400ft (121m) and reach speeds of 30mph (48kph).
All unmanned aircraft have to be licensed to conduct aerial surveillance work after the law changed at the start of 2010.
They need CAA permission to fly within 164ft (50m) of people and within 492ft (150m) of buildings.
The military-designed equipment is directed through a remote control, which is used by an officer on the ground.