Watchdog MPs have called on the government to create a new select committee to probe value for money in "highly confidential" areas of public spending.
The new Public Accounts Committee report says that current arrangements for parliamentary oversight of spending on the nation's nuclear deterrent and UK Special Forces – as well as funding for other areas of foreign, trade and security policy – contain "scrutiny gaps".
Particular areas of concern in the report are those areas of spending that fall outside the remit of the statutory Intelligence and Security Committee, the Defence Select Committee and the Joint Committee on the National Security Strategy.
MPs said that while procedures currently exist for such spending to be examined, the arrangements do not allow for detailed, routine scrutiny on behalf of parliament.
In addition to a lack of transparency and a lack of scrutiny, the PAC report says the current arrangements make it harder for MPs trusted with one-to-one briefings to hold government to account than would be the case for a committee.
The report acknowledges that certain types of government expenditure need a scrutiny approach that is "commensurate with their sensitivity".
But it adds: "Extrapolating from government performance elsewhere, it is likely that there are problems with poor delivery or project performance which parliament can neither see nor exercise positive influence over."
In relation to the UK's nuclear deterrent, the report states that National Audit Office has identified that the Defence Nuclear Organisation is now forecast to spend £99.5bn over the next 10 years, according to December's Equipment Plan 2023–33 report. The figure is an increase of 62% from the previous year.
PAC said that the MoD's annual report on the nuclear enterprise is a short, high-level document with little detail, "given the scale of expenditure and size of the programmes involved".
It added that the NAO's earlier Equipment Plan 2021–31 report noted that the MoD was planning to spend more than £1.1bn in support of the UK Special Forces, to enable the acquisition of additional equipment from 2025.
MPs said that despite the apparently high expenditure level, the MoD resisted requests from the Defence Select Committee to provide more information. The department said "strict controls" were required on publication of information about the security of UK Special Forces personnel, equipment and techniques.
PAC said the approach contrasted to that taken by the United States Special Operations Command, which publishes information on its website and gives evidence to Congress. The report said committees of both US Houses of Congress were able to hold open and closed sessions on defence, intelligence and other sensitive areas of expenditure.
MPs added that the Norwegian parliament had a committee that can receive reports on classified defence expenditure.
The PAC report says the committee it proposes may wish to take evidence and correspond in private, but calls for it to be have "appropriate powers and safeguards to enable careful, consistent and timely scrutiny".
MPs added that the committee should have assistance from the NAO and other specialists to conduct its work.
They are calling for the committee to be created as soon as possible, and certainly before the dissolution of parliament for the looming general election – which must take place by January 2025.
Committee chair Dame Meg Hillier said MPs' ability to scrutinise sensitive government spending was being hampered in a way that could not be justified.
"Parliament must no longer see through a glass darkly on whether value for money is being secured on confidential expenditure," she said.
"There are of course sound reasons why certain areas of spending must be examined in a manner appropriate to their sensitivity. Such sensitivity is all the more reason why the processes around its scrutiny should be made robust.
"A new select committee would address the current gaps in how such matters are scrutinised, and the PAC would be pleased to work with the government to take this proposal forward."
An MoD spokesperson said the nuclear deterrent and UK Special Forces were operations that required "the highest levels of discretion" but were accountable to parliament.
"We recently outlined the full scale of the Defence Nuclear Enterprise’s work, including how we will deliver the programmes necessary to strengthen our nuclear deterrent, supporting tens of thousands of UK jobs in the process and ensuring value for money for the taxpayer," the spokesperson said.
"These are two of the most critical areas of government spending and we note the Public Accounts Committee’s report and recommendations."