The Ministry of Defence has rejected observations made in a report, which questioned its "inability to control costs in its large programmes".
The Public Accounts Committee (PAC) argues in its report that the Russian invasion of Ukraine was a reminder of the "risks and responsibilities" which come with the UK's membership of NATO.
And MPs have warned that the UK Armed Forces may lack the "modern battle-winning capabilities" they need to meet the demands of future warfare.
While other countries were developing new capabilities such as hypersonic weapons, the committee said the MOD was forced to address "capability gaps" in the existing forces.
Despite a £16.5bn budget increase in the four years to 2024-25, the PAC – which examines the value for money of Government projects, programmes and service delivery – expressed frustration at the "complacency" within the MOD over the affordability of its equipment plan.
The Government's Integrated Review (IR) of foreign policy and defence last year identified Russia as "the most acute threat" to national security.
However, the committee said it was concerned that recent events meant the IR still "downplays" the scale of the threat Moscow poses to the UK's interests.
"We are concerned that the department may not have identified all the modern battle-winning capabilities our Armed Forces need, and also that it is not developing its existing large programmes with sufficient urgency," the PAC report said.
A defence spokesman has, however, rejected the observations made in the PAC's report.
"We entirely reject the observations made in the PAC Report. It is wrong to say we haven't identified the modern battle-winning capabilities our Armed Forces need.
The committee said that while the MOD was beginning to develop next-generation systems, there was "relatively little money" to exploit promising research during the coming decade and a lack of clarity as to whether they would be truly "battle-winning".
It noted that the new radar for the RAF's Typhoon fighter jets was not due to enter service until 2030, even though it was first announced in 2015 and that development work had begun much earlier.
Ministry of Defence response:
"Our affordable plan for defence outlines £238bn of investment over the next 10 years including a £24bn uplift in the current spending round," said a spokesperson for the MOD.
"We are delivering ongoing fundamental change to drive value in defence procurement, including enhanced management of projects and greater agility.
"The speed of response and depth of leadership being provided by the UK in response to the invasion of Ukraine has been widely recognised by the international community," they added.
Watch: £2bn-plus to boost Dreadnought nuclear submarine programme.
The committee also questioned the overall affordability of the equipment plan which depended upon delivering billions of pounds of future cost reductions but with no plans as to how they would be achieved.
It expressed concern that a Treasury "contingency" for the new Dreadnought class of nuclear submarines – which will carry the UK's Trident nuclear deterrent – was being seen as a "blank cheque" by the MOD "freeing it from the need to control costs".
PAC chair's comments
Dame Meg Hillier MP, chair of the Public Accounts Committee, said: "The MOD trumpeted a step-change in this year's Equipment Plan after the Integrated Review, with new priorities and a huge cash injection – but the invasion of Ukraine has cast in stark relief the realities of current and future warfare.
"Year on year we report on the MOD's failures to balance its budgets and the immense costs racking up on current projects that are delayed by years.
"We can find little cause for optimism that the MOD will become a better custodian of the taxpayers' money that needs to be spent developing next-generation capabilities.
"Senior officials appear unable to recognise the poor state of affairs in MOD's procurement or the deep-rooted issues that undermine our confidence that it will actually get a grip on the situation.
"A diminished role in global security, and enhanced risk to our national security and the service personnel defending it, are the unacceptable costs of the Ministry's ongoing and repeated failures."