The Committee wants more information about the purchase of F35s (Picture: MOD).
The Armed Forces face a funding black hole of at least £7 billion in plans for kit over the next decade, according to the Commons public spending watchdog.
In a scathing report, MPs on the Public Accounts Committee said the Ministry of Defence (MOD) "lacks the capability to accurately cost programmes within its equipment plan".
The committee predicts the actual shortfall in funding could reach nearly £15 billion by 2028.
The Commons financial watchdog accused the Government of dithering over which projects to fully finance, cancel or scale back. It said the MOD has no "coherent and credible plan" to monitor and deliver savings.
The cross-party committee concluded the 10-year equipment plan remains unaffordable as the Government continues to delay decisions on its priorities: The report added:
"We remain sceptical that the department is close to reconciling what it says it needs with the funding it has available."
Meg Hillier says she is 'not convinced' the MOD's equipment plan is achievable.
The MOD insisted that it would deliver this year's element of the equipment plan within budget, and was addressing the "financial challenges posed by ambitious, complex programmes".
The Committee demanded more information on the risks associated with major projects, including the purchase of F-35 stealth jets and Type 31e frigates.
The committee's chairwoman Meg Hillier said:
"In terms of poor financial planning, the Ministry of Defence is a repeat offender."
She said that progress in addressing concerns raised by the committee in May 2018 had been "woeful", adding:
"The MOD simply cannot afford everything it says it needs and it is not acceptable for officials to continue deferring decisions that have a bearing on its current affordability gap and longer-term risks.
She went on to say, "A department that is unwilling or unable to take the action required to help it live within its means is failing taxpayers, who rightly expect Government to deliver the best possible value for their money."
A MOD spokesman said:
"We are confident that we will deliver the equipment plan within budget this year, as we did last year, as we strive to ensure our military have the very best ships, aircraft and vehicles."
The spokesman went on to say, "At the same time, we are addressing the financial challenges posed by ambitious, complex programmes, after securing a £1.8 billion financial boost for defence and reducing forecast costs by £9.5 billion through efficiency savings.
"We are grateful for the PAC's report on the equipment plan, and we will carefully review all of its recommendations."