Three nuclear submarine programmes are in different stages of construction at Barrow's shipyard with an expanded workforce.

But a think tank has called for more boats to be added to the upcoming Dreadnought and AUKUS fleets to address future challenges for the Royal Navy.

Four Dreadnought submarines are being built to form the UK's at-sea nuclear deterrent but the think tank has urged the Government to add at least one more.

The Council on Geostrategy said it should act as an attack submarine.

The think tank has also suggested ordering 12 AUKUS submarines, which will replace the Astute programme of boats.

In the think tank's report, A More Lethal Royal Navy, authors William Freer and Emma Salisbury said: "To meet its environmental commitments and maximise the opportunities of Net Zero, the UK also generates a growing percentage of its electricity from offshore wind farms. Guarding these maritime interests is the Royal Navy, as the custodian of the British nuclear deterrent which acts as the ultimate guarantor of the nation.

"But a number of hostile states and competitors have grown stronger at sea over the past decade, countries which have sought to subvert the international order.

"To meet this challenge, it is widely acknowledged that Britain needs a larger and even more capable fleet."

Making the case for more Dreadnoughts submarines, the report said: "Procure at least one additional Dreadnought class boat to insure against delays in the design phase of the AUKUS programme.

"This fifth vessel can be operated as a conventionally armed nuclear powered attack submarine (SSGN) designed to carry a large payload of strike missiles.

"This would both amplify Britain’s conventionally armed submarine force (and act as cover to the SSBN [ballistic missile submarine] fleet should one of those boats face issues) and keep the submarine industry’s workforce active, abating the risk of delays to the AUKUS programme from the need to rebuild the workforce – as happened during the gap between the commissioning of the Vanguard class and Astute class."

The Conservatives have pledged to increase the UK's defence spending to 2.5 per cent of gross domestic product by 2023. Labour has said it would provide the same spending boost 'soon'..