The Royal Navy's Type 45 destroyers are so noisy they can be heard by Russian submarines 100 miles away, a former senior naval officer has claimed.
Rear Admiral Chris Parry, a former director of operational capability at the Ministry of Defence, said the ships sounded like a "box of spanners" underwater.
Admiral Parry, who wrote the original concept paper for the vessel, told The Sunday Times that the noise meant their movements could be picked up at long range by Russian submarines.
He said the MoD appeared to have ploughed all its resources into the ship's air defences "without thinking about the anti-submarine element" as it believed the threat had diminished since the end of the Cold War.
However the Russians have since developed the new Kilo-class hunter-killer submarine, known as the "black hole" because it is so quiet.
"During the Cold War, I would say the ships I was in were the equivalent of a whisper.
"These ships now are the equivalent of shouting at somebody," Admiral Parry said.
"It's crazy. Noise suppression has probably been the biggest dirty secret since the end of the Cold War that people have been cheerfully ignoring."
The MoD however said the Type 45 was primarily designed for air defence and that "stealth" was not a "premium requirement".
The noise issue with the Type 45 was one of a number of claimed flaws with major military equipment programmes identified by The Sunday Times.
They include the Army's new Ajax light armoured vehicles, which were said to be too big to fit inside the RAF's main A400m transport aircraft without being partly dismantled.
The vehicles are intended for rapid deployment but the paper said experts believed they would have to be accompanied by a crane if they were moved by air.
However the MoD said that, as was common with armoured vehicles, Ajax was designed to be "modular" and that parts could easily be removed and refitted.
An MoD spokesman said: "Britain's defence budget is the biggest in Europe and it is growing every year.
"We are focused on maintaining an affordable programme and getting the best value for the taxpayer to deliver the cutting-edge kit our armed forces need to keep Britain safe."