Military experts said the order is really costing pounds 3bn, as four conventionally- powered Upholder class submarines, which cost pounds 1bn, were originally designed to do many of the same jobs but were then declared surplus. They are still at Barrow-in-Furness, in Cumbria, waiting to be sold.
There is also doubt whether nuclear-powered vessels, designed to hunt Soviet submarines in the North Atlantic are necessary for the operations Britain is likely to conduct when the Astute-class boats come into service in 2005.
But MoD sources said the new submarines will be much more economical, as they will never need to be refuelled during their 25-30-year life.
The submarines are not being built with separate accommodation for women. The MoD had previously said women would serve in submarines, when suitable accommodation was available.
Of the 100 berths on board the new submarines, 18 will have to be shared between men working shifts, the procedure known as "hot bunking".
Defence Procurement Minister James Arbuthnot told Parliament the order would be placed with GEC-Marconi as the prime contractor responsible for designing and building the submarines and their equipment, and maintaining them for the first four-and-a-half years.
It is the first time major warships have been built on a prime contractor basis. Mr Arbuthnot said the order will help sustain about 7,000 jobs at the Vickers Shipbuilding and Engineering (VSEL) yard at Barrow-in-Furness, and in Edinburgh, Glasgow, Derby, Bath and Bristol.
GEC-Marconi designed the submarines in competition with VSEL. But then Lord Weinstock, GEC's managing director, bought VSEL, enabling the MoD to combine the benefits of innovative design from GEC-Marconi - these are the first submarines they have designed - and VSEL's shipbuilding experience.
At 6,000 tonnes, the new Astute Class submarines will be able to carry land-attack cruise missiles with conventional warheads which can be fired from their torpedo tubes.
The Navy currently has four ballistic missile-firing Vanguard submarines and 12 nuclear-powered hunter-killers; five of the ageing Swiftsure class and seven Trafalgars. The Astutes are to replace the Swiftsures, so another two will be ordered later, unless the next government decides they are not needed.
n GEC-Marine VSEL received a big jobs boost with the news last night that the United States has awarded it a pounds 300m contract.
The company won the two-and-a-half-year contract to build light artillery, the Ministry of Defence announced. The company, with its US partner Cadillac Gage, will supply the US Marines and US Army with 155mm howitzers.
The contract includes an initial production of 190 guns which will be ready for active service by the year 2002.
If the howitzers are satisfactory, the whole programme could include up to 1,000 guns and be worth a total of pounds 650 m. The contract includes an initial production of 190 guns to be ready for active service by 2002.Reuse content