The UK’s armed forces are facing a £21bn funding shortfall over the next decade, a critical report from parliament’s spending watchdog has warned.

The public accounts committee said the Ministry of Defence (MoD) “simply does not have enough money to buy all the equipment it says it needs” and accused it of not being clear with politicians or the public about the financial risks.

The warnings have emerged as Jeremy Corbyn prepares to call on Friday for navy shipbuilding contracts to remain in the UK.



In a speech in Glasgow, aiming to underscore that Corbyn takes an interest in defence, the Labour leader will insist that three new Royal Fleet Auxiliary vessels must be built in British shipyards.

Corbyn will say: “Workers in British shipyards, from Plymouth to Rosyth, share a proud tradition – building the best ships in the world.

“But the Conservative government is trashing that tradition by offering up the Ministry of Defence’s most recent contract for three new fleet solid support ships to overseas companies to build abroad.

“This decision is wrong. Today we are calling on the government to guarantee that these three new ships for the Royal Fleet Auxiliary will be built in domestic shipyards.”

The PAC inquiry said the “affordability gap” in the MoD’s equipment plan for 2017 to 2027 had worsened since it reviewed it last year, and criticised officials for still being “unable to determine the size” of it accurately.

The most conservative estimate is £4.9bn, rising to a worst-case scenario of £20.8bn more than the 10-year £179.7bn equipment budget, they found.



This budget accounts for 40% of the MoD’s planned spending in that period.

The PAC’s 2017 review found a budget shortfall of £7bn.



The report criticised the plan as “not realistic”, and identified weaknesses in controlling costs.



The construction of the next generation of nuclear missile submarines and the F-35 fighter programme were among those singled out for criticism.



The report, released on Friday, said the biggest concern was over a need to bring forward some of the costs of building the next generation of nuclear missile submarines, the £31bn Dreadnought class, plus its nuclear warheads.



The committee heard evidence that while the cost of the four planned submarines may not increase, some of the money may need to be spent sooner than previously thought, putting extra strain on the budget.



MPs also highlighted a failure to include the cost of buying an entire new class of frigate for the Royal Navy, the F31e, in the original equipment plan in 2017.



That plan was also missing £9.6bn of “additional costs” but the MoD had been unable to say what they were, the report found.

The report also highlighted a lack of “flexibility” in spending that could undermine the armed forces’ ability to combat new threats, such as cyber-attacks and artificial intelligence, because so much money is tied to large-scale, long-term projects.



It said the Modernising Defence Programme, announced by the defence secretary, Gavin Williamson, in January, should explain how it intended to build long-term capability yet retain “sufficient flexibility to respond to changes in the defence landscape”.