Britain is "no longer capable" of running a nuclear submarine programme after "catastrophic" failures pushed it to the brink, a former Navy chief has warned.
In an extraordinary critique, Rear Admiral Philip Mathias said the UK's "silent service" was facing an "unprecedented" situation that it was "highly unlikely" to recover from without a "radical" intervention.
The former director of nuclear policy at the Ministry of Defence (MoD) said delays in building new attack boats had reached record levels and had driven up the duration of patrols for crews from 70 days during the Cold War to more than 200 now.
This had led to the "shockingly low availability" of submarines to "counter the Russian threat in the North Atlantic", the retired submarine commander warned.
The admiral, who led the Trident value for money review in 2010, called for Britain to pull out of the multi-billion "Aukus" defence deal with America and Australia to build 12 new nuclear submarines.
"The UK is no longer capable of managing a nuclear submarine programme," he said.
"Dreadnought is late, Astute class submarine delivery is getting later, there is a massive backlog in Astute class maintenance and refitting, which continues to get worse, and SSN-Aukus is a submarine which is not going to deliver what the UK or Australia needs in terms of capability or timescale.
"Performance across all aspects of the programme continues to get worse in every dimension."
He added: "This is an unprecedented situation in the nuclear submarine age. It is a catastrophic failure of succession and leadership planning."
The Navy's fleet of Astute submarines is already facing significant problems, with many having been stuck in port for years. Out of the seven planned, only six are in service.
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HMS Ambush is currently inactive, having spent a staggering 1,222 days - more than three years and four months - in port, according to defence analysts.
Sister vessels Artful and Audacious are currently undergoing sluggish maintenance programmes, having both spent more than 950 days out of action. Astute and Anson are also in port.
HMS Agamemnon, the sixth and penultimate vessel, entered service in September during a commissioning ceremony led by the King, with ministers hailing it a "truly remarkable manufacturing feat".
"The uncomfortable truth is that she took over 13 years to build, the longest ever construction time for a submarine to be built for the Navy," Rear-Adml Mathias said.
Russia, meanwhile, continues to pressure the Navy, having ramped up its activity in UK waters by more than 30 per cent, John Healey, the Defence Secretary, has warned.
Vladimir Putin, the president of Russia, last week intensified his aggression by claiming he was ready to go to war with Europe.
The UK's nuclear-armed submarine fleet is critical to defending the country and deterring Russia and other dangerous states from using weapons of mass destruction.
The fleet of four Vanguard stealth boats carry Britain's nuclear missiles, with one vessel always patrolling the seas at any time.
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Each of the submarines can carry up to 16 Trident 2 D5 60 ton ballistic missiles all armed with up to eight individual warheads, the combined destructive power of which dwarfs the bomb dropped on Hiroshima in the Second World War and would wipe out millions of people.
However, the boats have faced issues in the past during launch tests. In 2016, one of the 44ft Tridents fired from HMS Vengeance veered off course and reportedly self-destructed.
Then, on January 30, 2024, at Port Canaveral, Florida, a missile launched from HMS Vanguard misfired and landed back in the sea.
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In his critique, Rear-Adml Mathias said Britain's next generation of nuclear weapon boats, the Dreadnought-class, should be the "last class of nuclear-powered submarines that the UK builds".
He added the Aukus programme should be "cancelled now", with the money instead spent on better "cost effective" ways of delivering the same capability but with cheaper tech, like aerial drones or smaller unmanned submarines.
The naval commander pointed towards historic cuts in defence spending, repeated changes to how nuclear submarine programmes are delivered and a "huge failure" to manage key personnel as contributing factors to the decline.
But he also criticised the role of industry giants for delays to programmes.
He added not a single of the UK's 23 decommissioned nuclear boats had been dismantled since the first, HMS Dreadnought, left service in 1980.
"This is an utter disgrace and brings into question whether Britain is responsible enough to own nuclear submarines," the admiral said.
A defence source insisted the "right people were in the right place" to continue to oversee Britain's nuclear programme.
The Ministry of Defence (MoD) said it was committed to delivering the next generation of nuclear submarines and that the Dreadnought programme remained on track.
The MoD added it was committed to the safe disposal of old boats and that it was a responsible nuclear operator, meeting the highest standards of safety, security and environmental protection for the current projects in Devonport and Rosyth and through planning for a future disposal capability in the UK.
A spokesman added: "We are unwavering in our commitment to renewing and maintaining the nuclear deterrent underlined by the biggest sustained investment into defence spending since the end of the Cold War.
"The Strategic Defence Review made clear the need for sustained investment across the Defence Nuclear Enterprise. This will see delivery of the most powerful attack submarines ever operated by the Royal Navy and the investment of £15bn this Parliament into our sovereign warhead programme."