Britain's armed forces need a significant hike in funding to meet the resurgent threat from states like Russia and fill existing "black holes" in their finances, a new parliamentary report has said.
The report from the Commons Defence Committee said the Government should start the process of moving the level of defence spending up from 2% to 3% of total GDP.
A cash injection on this scale would equate to additional funding of around £20 billion a year and bring investment in defence to levels similar to those seen between the end of the Cold War and the mid-1990s.
In its report, entitled Beyond 2 Per Cent, the committee warned that failure to finance the military on a sustainable basis makes it "very difficult" to implement a long-term strategy for Britain's defence needs.
A new settlement providing long-term strategic and financial stability is the "only solution" at a time when the UK faces a renewed threat from Russia, as well as increasing challenges from terrorism, extremism, cyber-warfare and the erosion of the rules-based international order, said the cross-party committee.
The report comes weeks ahead of the expected release of high-level findings from the Ministry of Defence's Modernising Defence Programme (MDP).
The committee congratulated Defence Secretary Gavin Williamson for extracting military spending from the remit of the Government's National Security Capability Review.
The NSCR's fiscally neutral nature risked deep cuts in parts of the armed forces - such as the potential loss of the assault ships HMS Albion and HMS Bulwark - and created the "perverse situation" that a review prompted by intensified threats could result in reductions in capability.
The "bold step" of establishing the MDP should allow ministers to deliver "the force structure necessary to meet strategic objectives rather than one that merely fits within straitened financial parameters", said the report.
The armed forces that emerge from the MDP must be supported by a "robust and sustainable financial settlement, which is not reliant on loose projections and unrealistic so-called efficiency targets to make the numbers add up".
The report warned of "serious deficiencies in the quantities of armour, armoured vehicles and artillery available to the British Army".
The lack of vehicle-mounted anti-tank weapons and self-propelled artillery, as well as the need for modernisation of rocket artillery left the Army "at serious risk of being outgunned by its Russian counterpart", it said.
Other defence needs identified by the committee included:
- Greater anti-submarine warfare capacity;
- The generation of a Royal Navy carrier group capable of protecting the new Queen Elizabeth-class aircraft carriers without depending on other states;
- The maintenance of the target strength of the regular Army at a minimum of 82,000 personnel;
- A layered air defence system to protect the war-fighting division.
Committee chairman Julian Lewis said: "The Secretary of State was right to remove defence from the National Security Capability Review which would otherwise have resulted in further disastrous cuts to the armed forces, and we endorse his efforts to obtain a better settlement for defence.
"The Government now needs to look beyond the 2% minimum on defence spending, and begin moving towards a figure of 3%, to place our defence policy on a sustainable basis to meet new threats and fill existing financial 'black holes'.
"Defence is constantly described as the first duty of government. The MDP is the Government's opportunity to show that it means what it says."
A Ministry of Defence spokesman said: "The UK maintains the biggest defence budget in Europe, we have been clear we will continue to exceed Nato's 2% spending target.
"The Defence Secretary launched the Modernising Defence Programme to strengthen our armed forces in the face of intensifying threats and, while we welcome the Defence Committee's preliminary report, we will not speculate on the outcome of the programme before we share our headline conclusions."