A project to deliver a unified computer system for Britain’s armed forces is running 18 months late and in danger of being seriously over budget unless the Ministry of Defence takes “concerted action”, says the public spending watchdog.

In a report on the Defence Information Infrastructure programme (DII), the National Audit Office on Friday will warn that the MoD has to roll out more than 6,000 computer terminals a month – double the highest average to date – if it is to meet its revised timetable.