A former First Sea Lord said the disclosure was "extremely worrying".  Lord West of Spithead said: “Clearly there is a major fault here. Initially people were saying these are teething problems and you always have teething problems with new ships. It is quite clear it is more than teething problems now."  HMS Duncan, the British Navy's sixth Type 45 Destroyer Photo: MoD/PA  "It is bad enough fighting your ship when people are dropping bombs on it and blowing bits of equipment out and you keep it going - that's what we're trained to do. You don't expect suddenly to lose all power when you are steaming along normally," he said.  • Royal Navy destroyer put to sea without missiles a 'disgrace'  The refits will include cutting holes in the sides of the ships to fit them with new generators.  The 8,000-ton air defence destroyers have a crew of 190 and are designed to shield the rest of the fleet from air or missile attack. They will play a vital role in defending Britain’s new aircraft carriers when they are completed.  But their innovative power and propulsion system, which sees the ships’ shafts and the rest of its systems powered by the same gas turbines, has struggled with blackouts.  In 2014 HMS Dauntless cut short an exercise by two days and had to return to port after losing power.  Her sister ship, HMS Daring, needed emergency repairs in Bahrain in 2012 while deployed to the Gulf. Reports said the ship encountered propulsion problems while on patrol off the coast of Kuwait.  In 2009, HMS Daring also lost power in the Atlantic after a visit to New York and had to go to Halifax shipyard in Canada to be fixed.  HMS Defender travels past the Titan Crane as she makes her way up the River Clyde back to Glasgow in 2013 Photo: PA  Richard Scott, naval consultant at IHS Jane's, said: “Initially there was the view that it was teething trouble and they would get it right. What’s happened latterly very much acknowledges that after a period of six or seven years, the power system is still very fragile.”  The staggered refit, which will begin in 2019, will putted added pressure on the fleet, which many Naval commanders say is already overstretched.  • Boost to Portsmouth as BAE wins contract to restore Navy destroyers • What kit do Britain's Armed Forces have, what do they want, and what are they getting?  He said: “The fleet is already stretched. They are going to have to make sure that during the maintenance periods where they do the upgrades, the downtime is as short as possible.”  Type 45s have worked alongside the US Navy in the Gulf for the past year, protecting their aircraft carriers while they launch air strikes against Islamic State in Iraq and Levant (Isil).  Mr Scott said the Navy was worried about its warships breaking down in front of its closest ally.  He said: “The concern is that we have some kind of mechanical breakdown, which would be very embarrassing operationally and also in terms of the Navy’s standing with its closest ally.”  A spokesman said: "The Type 45 destroyers are hugely capable ships and have consistently made a difference to our safety and security.  "In our defence review last year we committed to improving the Type 45's power and propulsion system through a series of machinery upgrades during planned maintenance, which will ensure increased availability and resilience over the life of the ships."  HMS Daring fires a Sea Viper air defence missile Photo: MBDA  A spokeswoman for BAE Systems, which builds the ships, said: "The Type 45 Destroyers are among the world's most capable air defence Destroyers, able to carry out a wide range of operations for the Royal Navy.  "We are working collaboratively with the MoD and industry partners to deliver improvements to the power generation capability of the Type 45 Destroyers."  Rolls-Royce, which makes the WR-21 gas turbines, said: "We are committed to supporting the WR-21 in service and have recently opened a new overhaul and test facility in Bristol.  "We continue to work with the MoD on upgrading the performance of the propulsion system."
Ministry of Defence confirms that six Type 45 destroyers are to undergo refits   as they keep breaking down