SPY planes are set to take to the skies over Essex within two years to help combat illegal immigration and drug smugglers.

Essex Police have teamed up with their colleagues in Kent to customise spy drones, which are used by the Army in Afghanistan to gather intelligence about the Taleban.

Unmanned aircraft systems can read a number plate from 20,000ft and criminals will not know they are under surveillance.

The drones can also stay in the air for 15 hours, far longer than a police helicopter or other surveillance aircraft.

Police have declined to say how much the project would cost.

Last year, Essex Police Authority set aside £19,000 to investigate drones working with the UK Border Agency, the Maritime and Coastguard Agency, the Marine and Fisheries Agency and defence company BAE Systems.

The drones could also fly over major events, such as the V Festival, or major incidents.

Chief Insp Richard Watson, of Kent Police, the force leading the project, said: “Unmanned aircraft have the potential to perform a significant role, and it is important to work alongside authorities such as the Civil Aviation Authority, and companies like BAE Systems, to make sure any introduction of these systems is done responsibly.

“It makes good sense for us all to contribute to it and share the costs and benefits.”

BAE said it is looking to adapt two main drones for every day use, the HERTI, said to be best for border and coastal patrol, and the GA22 for hovering above major events.

With a wing span of 12.6m, the HERTI could travel at between 90 and 120 knots and use around ten litres of fuel an hour.

Andrew Mellors, head of civil autonomous systems at BAE, said: “The drones can be instructed to search for and detect certain suspicious behaviours and alert the maritime authorities immediately, who can take action to engage a vessel.

“The partnership is aimed at making the most effective and efficient use of resources, and ensuring drones are introduced into use responsibly.”