The scheme has been commissioned by the Defence Communication Services Agency, which deals with all communications affecting the UK's armed services, including systems used in recent operations in Iraq.
The agency intends to consolidate its operations at the site, which is in Corsham in Wiltshire. The location will house 5000 DCSA personnel.
The contract requires the construction of a headquarters building, but also the decommissioning of 200 acres of tunnels, caverns and bunkers beneath it.
This subterranean space was once part of mine workings for Bath stone, a material used in Roman and Georgian architecture. In the Second World War it became an aircraft factory and a munitions store; during the Cold War it became an RAF operations control point, as it was deemed invulnerable to a nuclear strike.
The contract requires the construction of an HQ – and the decommissioning of 200 acres of tunnels
A spokesperson for the agency said the mine workings could not be redeveloped because they would contravene Health and Safety Executive regulations, but that they might be used as a storage site for archives.
The source added that a nearby site at RAF Rudloe Manor is being considered for redevelopment as a business park after the headquarters is opened.
A decision on the preferred bidder is expected by next May and the final decision will be made in November next year. Work would then start in 2005, with the construction process scheduled to last up to 30 months.