The UK Ministry of Defence has signed a contract with BAE Systems to begin construction of the fifth Astute Class submarine and start the procurement process for a sixth vessel.

Secretary of State for Defence Bob Ainsworth said the MoD had signed a contract to take the project into its next important stage – the assessment phase – to consider the vessel’s design.

During the assessment phase, a team led by BAE Systems Surface Ships in cooperation with the MoD will consider design proposals for the Type 26 combat ships.

According to the defence secretary, the government will proceed with the initial build of Astute Boat 5 and long-lead procurement activities associated with Astute Boat 6, at a total cost of over £300m ($446m).

The 7,400t vessels will undergo a wide range of missions including anti-submarine and anti-surface warfare, command and control, protection of high value shipping, surveillance, intelligence gathering, humanitarian aid, disaster relief and evacuation of non-combatant forces.

The Astute Class submarines will replace the aging Type 22 Swiftsure and Type 23 Trafalgar Class submarines.

Work will be carried out at the shipyard in Barrow-in-Furness.

The first of class Astute attack submarine HMS Astute is undergoing sea trials, the second submarine HMS Ambush is due to be launched in 2011, while HMS Artful and HMS Audacious are both advanced in their construction.