A LEAK onboard Britain’s most expensive aircraft carrier – the £3 billion HMS Queen Elizabeth – which was described by the Ministry of Defence (MoD) as a “minor issue” could have resulted in the death of four crew members, The National has learned.

The 65,000-tonne vessel, Britain’s biggest and most powerful warship, was this week forced to return to Portsmouth early from five weeks of sea trials after a major leak onboard.

A spokesperson for the MoD told Forces News that because of a “minor issue with an internal system on HMS Queen Elizabeth, the ship’s company were required to remove a small volume of water from the ship”, and that an investigation was under way.

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However, an insider told The National: “The Royal Navy is playing down the extent of the flood to a criminal degree.

“Four crew members were very nearly killed by a known safety fault.”

They said the high pressure saltwater (HPSW) ring main parted and flooded thousands of tonnes of water into the ship.

The carrier has a total of 16 decks – nine from the hull to the flight deck and seven in its two islands.

It was claimed that two of them on levels five and six were almost lost.

“The weight of the water caused decks and bulkheads to buckle under the pressure,” said our source.

“Doors were crushed into their frames trapping personnel and ladders warped as the decks buckled.”

They said the leak happened because the ring main had been fitted with couplings they described as a “temporary measure” which are used to quickly repair damaged pipework and were never designed to be permanent.

“However to save cost in the building process they were fitted instead of welding the pipes across water, oil and even fuel systems,” we were told.

“This is the third and most serious incident on HMS Queen Elizabeth involving these couplings failing.

“While the ship was in three parts in three yards this was identified as a major threat to ship safety and an emergency change request (ECR) was put in to change them out and weld the pipe work properly.

“However, to save costs once again, only a few were changed and those on straight stretches were left.

“It was one of these that failed last night.”

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The insider said the couplings were due to be changed while the Queen Elizabeth was in Rosyth, but the vessel left six months early to go to Portsmouth.

They added: “The same issue still remains on HMS Prince of Wales which is sitting in Rosyth. These couplings are fitted on all systems … these same temporary couplings are in place on the aviation category fuel systems too. If one of them were to split under pressure lives will be lost. Plain and simple. I would suggest this issue must be resolved immediately to ensure the safety of our sailors.

“This is a clear and known about risk across both carriers.

“It is criminal that it is being ignored.”

Douglas Chapman, the SNP’s Westminster spokesperson for defence procurement and nuclear disarmament, whose constituency includes Rosyth, said the incident was a “wake-up call to the MoD”.

He called for a full investigation into the allegations.

“It is extremely concerning to hear about this incident whilst HMS Queen Elizabeth has been out at sea and hundreds of crew members have been on board,” he said.

“This must have been a frightening experience for everyone involved.

“Cost-cutting measures should never be used when building ships, especially on a flagship aircraft carrier such as the HMS Queen Elizabeth.

“This is apparently the third time one of these couplings has failed – the first time should have been enough to raise some serious questions around safety. I hope this is a wake-up call to the MoD that it cannot sacrifice the safety of crew members in favour of cost-cutting.

“There also needs to be a full scale investigation into whether this cost-cutting measure has also been used in building the HMS Prince of Wales, which is currently being built in Rosyth, in my constituency.”

Chapman added: “If the MoD is serious about defending the waters around the UK, ships like this need to be built to the best standard possible.”

We asked the MoD to comment on specific aspects of the claims, but a spokesperson would only say: “We do not recognise the 250 tonnes of water figure [as reported by Forces News], it is impossible to get an exact figure but it is substantially less.

“There was no risk of service personnel drowning as a result of this leak.”