The UK government is to buy at least 12 new fighter jets that can carry nuclear bombs, the prime minister has announced.

Sir Keir Starmer said at the Nato summit in The Hague that the new US-made F-35A jets would join Nato’s airborne nuclear mission.

“We will procure at least 12 and we will make these aircraft able to bear nuclear weapons if necessary,” said the prime minister, adding the procurement was in “response to a growing nuclear threat”.

Downing Street says the move is “the biggest strengthening of the UK’s nuclear posture in a generation”.

The new F-35A jets can still carry conventional weapons, but have the option of being equipped with US-made nuclear bombs.

Nato’s airborne nuclear mission involves allied aircraft being equipped with American B61 bombs. Seven other countries, including the US, Germany and Italy, already use the jets.

The use of nuclear weapons would require the authorisation of Nato’s nuclear planning group as well as the US president and British prime minister.

The US has already pre-positioned stocks of B61 bombs in Europe. Justin Bronk of the defence think tank Royal United Services Institute (RUSI) said the US would still control their release and use in the event of a war. That may prove contentious with the UK being reliant on the US.

During an urgent question in Parliament on Wednesday, Conservative MP Lincoln Jopp asked whether a dual-key arrangement would be in place regarding weapons deployed from the aircrafts, “namely the Brits can’t use it without the American say-so”.

Border Security Minister Dame Angela Eagle said the current decision is about joining the Nato nuclear mission which would require the agreement of all 31 allies.

“The UK will also always retain the right to participate, or not to participate, on the basis of that governance arrangement,” she said.

Prime Minister Sir Keir Starmer 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.”

Defence Secretary John Healey told BBC Breakfast on Wednesday that the investment would “strengthen the Nato-collective deterrent that comes from having this nuclear capability”.

Speaking in The Hague ahead of a Nato summit, Healey said the programme would support 20,000 jobs and more than 100 companies across the UK in the supply chain.

Nato secretary-general Mark Rutte called the announcement “yet another robust British contribution to Nato”.

The new fast jets will be based at RAF Marham in Norfolk.

The decision to buy F-35A jets will be seen as a victory for the RAF – which has long been lobbying for a longer range fighter that can fire a larger variety of bombs and missiles.

The F-35B variant, currently operated by the RAF and the Royal Navy’s Fleet Air Arm, has a shorter range and can carry fewer weapons.

With its short take-off and vertical landing capability, the F-35B can operate from the Royal Navy’s two carriers, HMS Queen Elizabeth and HMS Prince of Wales.

F-35As operate from conventional runways.

Britain currently only has one delivery system for larger strategic nuclear weapons – launched from its Vanguard class submarines via Trident ballistic missiles.

While the Trident missiles are made and maintained in the US, the warheads on the missiles are made and maintained in the UK. Successive governments have insisted that their use would not be dependent on the US – hence it is described as Britain’s “independent deterrent”.

RAF jets were capable of carrying smaller tactical nuclear weapons until 1998 – when the UK-designed and made WE177 bombs were retired from service.

Mr Bronk said it will take time for the RAF “to get back in the nuclear game”. He added the most obvious benefit for the UK buying F-35As will be their longer range and the fact they can carry a wider range of conventional weapons.

The decision follows the Strategic Defence Review, which Defence Secretary Healey said “confirmed we face new nuclear risks, with other states increasing, modernising and diversifying their nuclear arsenals”.

And on Tuesday, the government published a national security strategy in which it said the UK should “actively prepare for the possibility of the UK homeland coming under direct threat, potentially in a wartime scenario”.

Sir Keir has pledged to meet a new Nato target to spend 5% of the UK’s GDP on national security by 2035.

At the Nato summit, 32 member counties are expected to agree on the goal, which sees 3.5% going to core defence, with the rest on defence-related areas.