The former head of the UK Armed Forces has warned all three services are "too small" and that the Royal Navy's Type 45 Destroyers are arguably Britain's only counter-missile systems that could defend against a multiple missile attack of the kind that Russia is deploying against Ukraine.
General Sir Nick Carter, speaking to a group of MPs examining the readiness of the UK's Armed Forces at the defence committee, warned Britain could struggle to win a lengthy state-on-state war.
He voiced repeated concerns about the size of Britain's Armed Forces, which according to Ministry of Defence (MOD) figures in January 2023, places the number at just over 143,560 regulars, saying: "I think all of our Armed Forces have become too small.
"I don't think we have resilience in them to be able to be confident that if a peer-on-peer war broke out we would have any capability left after the first couple of months of the engagement."
Gen Sir Nick warned that the UK has a particular vulnerability around air defence, explaining how a multiple missile attack such as the ones Russia has been using against Ukraine would pose a considerable challenge for Britain.
He said: "The extent to which we've got a counter-missile system is debatable and arguably, the Type 45 is the only capability in the country that can deal with that sort of problem.
"So, a counter-missile defence, a sort of Patriot-type system, being used now in Kyiv – it's that sort of capability."
The Patriot missile system is being used by Ukraine to counter the threat of Russian air strikes.
Three countries have sent the Patriot to Ukraine – the US, Netherlands and Germany. Created by the United States, the Patriot system is used to intercept and destroy incoming cruise missiles and aircraft.
Standing for the Phased Array Tracking Radar to Intercept on Target, the Patriot's batteries consist of eight launchers, each with the capacity to fire four missiles.
The Royal Navy has six Type 45 Destroyers, considered to be the backbone of Britain's naval fleet, which it says are among the most advanced warships ever built, equipped with the Sea Viper missile.
Also known as PAAMS (Principle Anti Air Missile System), once airborne, the Sea Viper system can guide 16 missiles to targets that are as far away as 70 miles (113km), engaging multiple targets simultaneously.
Gen Sir Nick also recalled his concerns about the impact of the nuclear deterrent on defence finances during his time as the head of the Armed Forces.
He said: "I always used to worry as the Chief of the Defence Staff that the nuclear programme was taking up so much of our resource that we were diminishing our conventional deterrence as a consequence.
"And what we absolutely see with Russia, if you look at their ability to be able to manage escalation up and down levels of effort, it's much better than what we in the West have got."
The committee has set out to determine the main gaps in Armed Forces readiness and whether Government plans are sufficient to address these shortfalls.
MPs are continuing to hear from a range of witnesses for their report.