The Public Accounts Committee said the department’s funding shortfall could rise to more than £36 billion in the coming decade – many times the official estimate of £6 billion.
It also repeated criticism that the MoD has been increasing total bills by delaying projects to make short-term savings.
Committee Chairman Edward Leigh said: “Britain’s defence budget is fundamentally unaffordable.
“The MoD estimates it at £6 billion over the next 10 years but that figure depends on the assumption (surely optimistic) that there will be a year-on-year increase in funding of 2.7%.
“According to the NAO, even if cash spending on defence remains flat, then the projected deficit will be of the order of £36 billion. The deficit could be even higher than that. Matters have worsened to the point where the department will have to take difficult decisions, such as to cancel whole equipment programmes.” Read in full in the Daily Express.