Britain's new £6.2billion ($11 billion) aircraft carriers are vulnerable to relatively cheap long-range Russian and Chinese missiles, a report has revealed.
Multibillion-pound defence projects are at risk from technological advances by potential enemies of the UK, the think-tank study found, according to Daily Mail.
Missiles costing less than £500,000 ($889,000) each could "at least disable" Britain's new £3.1billion ($5.5 billion) HMS Queen Elizabeth, it claimed.
The report noted: "Key Western military assets had become vulnerable to targeting and disruption and destruction by long-range precision missiles to a degree that had hitherto been unthinkable."
It warns the Government has focused more on offensive systems over protective capabilities.
"There has been a growing imbalance within the attack-defence military equation, driven by the spread and speed of applicable technologies," it adds.
The report by the Royal United Services Institute (RUSI) lists Iran as an example, saying the country has long held anti-ship missiles from Russia.
It has also claimed to have developed its own Hormuz-2 supersonic, ballistic anti-ship missile, weapons which "must be seen as a key contextual element of British naval deployments".
The study says UK defence capabilities costing £16billion ($28.4 billion) a year are "increasingly vulnerable to low-cost, technology-rich weapons".
The Royal United Services Institute report names the most notable vulnerability as "increased peer and near-peer threat from Chinese and Russian long-range precision missiles".
It adds: "China and Russia appear to have focused many of their efforts on being able to put at risk the key Western assets that are large, few in number and expensive ... The advancing capabilities of potential adversaries of the UK should be a genuine concern."
For the adversary "it has become much cheaper to destroy major systems and platforms than to develop and build them, making large-scale attacks on a single target more likely".
Another area of concern is defences in space, where the UK has a significant satellite-building capability and makes extensive military use of space for spying and communications.
The report warns "the space-denial capabilities of peer and near-peer adversaries risked threatening critical navigation and communication capabilities".
The authors add: "The advancing capabilities of potential adversaries of the UK should be a genuine concern."
Co-author Professor Trevor Taylor, a professorial fellow at RUSI, said: "UK defence policy prioritises the capability to project force to areas of concern and to deter attacks on British assets and allies.
"The advancing capabilities of potential adversaries in Northern Europe, the Middle East and even East Asia need to be taken into account in reviews of UK defence policy and military tasks, British and Nato approaches to deterrence strategy, and the priorities for UK capability development."
Co-author Andrew Tyler said Britain must ensure "defensive posture and potential for recovery ...match our offensive capabilities".
Last month Britain's biggest ever warship, HMS Queen Elizabeth, squeezed out of the Rosyth basin in Scotland and set sail on her maiden voyage.
Once it is handed over to the Royal Navy it will boast 24 of the world's most advanced stealth fighter jets.
The F-35B Lightning II and its radar can track objects the size of snooker balls 20km away.
It will also have a modern-day Gatling gun known as Phalanx, which fires 20mm shells at a rate of 3,000 rounds a minute.