Essex Police have scrapped a plan to track down criminals from the skies using an unmanned spy plane.

The force invested £20,000 in a spy drone, but has put the aircraft up for sale without it ever being used.

The plan was announced in 2009 and it was hoped the aircraft would be used to survey major events, such as the V Festival, as well as combat illegal immigration and drug smugglers.

The force also intended to use it to film hostage sieges and firearms incidents, sending live footage to armed officers on the ground.

Drones can stay in the air for 15 hours and read a number plate from 20,000ft, so criminals don’t know they are under surveillance.

Robert Chambers, chairman of Essex Police Authority when the decision to buy the drone was made, said: “I’m quite happy it’s not going ahead because I’d rather see police on the ground looking at things.

“Buying it was probably one of the mistakes I made, so I hold my hands up and say sometimes you get it wrong.”

He said it was a shame money had been invested but, in the context of the authority’s budget, it only equated to “half a police officer”.

Essex Police needed permission from the Civil Aviation Authority to fly the aircraft, although it didn’t require a licence, and the authority said no application had been received.