The RAF should be given nuclear weapons to guard against the failure of the Royal Navy’s Trident, an expert has said, amid calls by ministers for more investment in defence.

The recent failure during test firing of a British Trident ballistic missile from a Royal Navy submarine has highlighted the risk of operating only one nuclear delivery mechanism.

The possibility of the RAF regaining the role of deploying Britain’s nuclear deterrent alongside the Royal Navy was boosted last week when the F-35 stealth fighter was certified to carry nuclear weapons.

Professor Andrew Dorman, of Chatham House, said: “An air-launched system would be the obvious choice for a second delivery mechanism and would bolster Nato’s deterrence forces.

“The F-35A would be the best aircraft. Typhoon could carry nuclear weapons, but it would take some integration work.

“The easiest way [for Britain] to get an air-launched nuclear weapon would be for the RAF to get F-35A.”

However, Professor Dorman said there was currently “no appetite” from the Government to look at any additional investment in defence, even though “they say we are living in a ‘1938 moment’”.

He said: “Apart from a few MPs, there is no campaigning for increased investment in defence. There are a lot of heads buried in sand.”

Calls for greater defence investment were amplified over the weekend after two serving ministers took the unusual step of using social media to call on Rishi Sunak to increase defence spending to 2.5 per cent of GDP.

The online article by Anne-Marie Trevelyan, a foreign office minister and former defence minister, and Tom Tugendhat, the security minister, had not been cleared by No.10.

Downing Street said social media commentary did not require prior permission.

“It’s clear to us that the UK needs to lead the way in increasing our own domestic defence and security spending commitments to 2.5 per cent and beyond,” the article, posted on Ms Trevelyan’s LinkedIn page on Friday evening, said.

“Former defence secretary Ben Wallace and prime minister Boris Johnson made inroads into growing our defence budgets, which had been shrinking in real terms for years. But that only filled the hole. Now we need growth.

“None of this is wasted cash. It’s investment in our own economy. And it protects our future economic security.

“The sad truth is that the world is no longer benign. Protecting ourselves requires investment. And effective investment means that our industrial complex must grow and strengthen at much greater pace than at present.

“We cannot turn on the complex platforms and weapons, which ensure military advantage overnight. We must start that growth now, invest at pace to support our allies and stay ahead of our adversaries.”

Defence spending did not feature prominently in last week’s budget.

Chancellor Jeremy Hunt reiterated a pledge to increase defence spending to 2.5 per cent of national income “as soon as economic conditions allow”.

The MoD has pledged to buy 138 F-35B jets, capable of vertical take off and landing, although money has only been programmed for the first 48.

No decision has been taken on potential future purchases of the “A” model, the variant that has been cleared in the US to carry the B61-12 thermonuclear gravity bomb.