Sir Keir Starmer will announce a major strengthening of Britain’s nuclear deterrent. The UK will purchase 12 new fighter jets and join NATO’s airborne nuclear mission in what Downing Street billed as “the biggest strengthening of the UK’s nuclear posture in a generation”.

The F-35A jets can carry conventional weapons and can also be equipped with nuclear bombs. The Prime Minister, who is attending the Nato summit in The Hague, said: “In an era of radical uncertainty we can no longer take peace for granted, which is why my Government is investing in our national security, ensuring our Armed Forces have the equipment they need and communities up and down the country reap the benefits from our defence dividend.”

The move will see the return of the Royal Air Force’s nuclear capabilities after the last British air-dropped nuclear weapon was withdrawn from service following the end of the Cold War.

The UK’s nuclear deterrent has been carried exclusively by the Royal Navy’s submarines since then.

Sir Keir added: “Supporting 100 businesses across the country and more than 20,000 jobs, these F-35 dual-capable aircraft will herald a new era for our world-leading Royal Air Force and deter hostile threats that threaten the UK and our Allies.

“The UK’s commitment to NATO is unquestionable, as is the alliance’s contribution to keeping the UK safe and secure, but we must all step up to protect the Euro-Atlantic area for generations to come.”

Defence Secretary John Healey said the decision followed the strategic defence review earlier this month, which “confirmed we face new nuclear risks, with other states increasing, modernising and diversifying their nuclear arsenals”.

NATO’s secretary-general Mark Rutte described the announcement as “yet another robust British contribution to NATO”.

NATO’s nuclear mission involves allied aircraft being equipped with American B61 bombs stockpiled in Europe, with seven nations currently contributing.

The use of nuclear weapons would require the authorisation of the alliance’s nuclear planning group as well as the US President and British PM.

NATO’s secretary-general Mark Rutte described the announcement as “yet another robust British contribution to NATO”.

NATO’s nuclear mission involves allied aircraft being equipped with American B61 bombs stockpiled in Europe, with seven nations currently contributing.

The use of nuclear weapons would require the authorisation of the alliance’s nuclear planning group as well as the US President and British PM.