The Ministry of Defence plans to develop robot submarines that can stay at sea and spy for up to three months.

The Royal Navy hopes that large unmanned submarines could conduct many of the tasks the existing fleet carries out, but with no risk to personnel.

At present, sensitive missions, such as “underwater data gathering” and “discrete payload delivery” require crewed vessels and the unmanned drones in service with the Royal Navy are currently too small for these tasks.

As a result, the MoD says it needs “a fully autonomous system of the size and capability of current manned platforms” and has launched a £2.5 million competition to attract proposals from industry.

The competition is expected to be run into the 2020s, with at least two years assigned to sea trials. The winning design must be capable of operating independently for a minimum of three months at up to 3,000 nautical miles from a home base. It must be able to deliver a two tonne payload, such as acoustic sensors and electronic warfare devices.

The MoD says the Extra-Large Unmanned Underwater Vehicles must be able to carry out a number of specific tasks including covert intelligence gathering, patrolling a pre-programmed area to identify hostile ships and deploying sensors to sit on the sea bed.