MPs and peers have warned they are sceptical about government promises to increase transparency around a secretive £1 billion anti-war fund.
Spending and strategy details for the project set up under David Cameron were kept from Parliament by ministers on the grounds of security concerns.
The Government has now said it will give private briefings on its work to the Joint Committee on the National Security Strategy (JCNSS).
But MPs and peers said they were "sceptical" about the move and warned they "cannot work in the dark" when assessing how taxpayers' cash was being spent through the conflict, stability and security fund (CSSF).
In 2016/17, £484 million of its total £1.127 billion budget was official development assistance (ODA), which counts towards the UK's target of spending 0.7% of national income on foreign aid.
But no information has been released explaining how the fund works, which countries money is spent in or which projects are funded.
No single minister is responsible or accountable.
Dame Margaret Beckett, who chairs the committee, said: "During our inquiry, the Government failed to provide the committee with sufficient evidence to judge whether the fund was reaching its potential.
"We are pleased that ministers have accepted that the JCNSS is the correct body to scrutinise this fund.
"We await the outcome of deliberations on ministerial accountability but expect that this will result in the appointment of a single cabinet minister to take responsibility for this fund.
"As the UK's aid spending is channelled through an increasingly broad range of government departments, clear transparency and accountability is vital.
"However, we cannot work in the dark.
"Without access to the National Security Council strategies for the fund, information about all the programmes and projects it has funded and a comprehensive breakdown of expenditure, we could not be expected to provide parliamentary accountability for taxpayers' money spent via the conflict, stability and security fund.
"Such information could be provided in private to the committee.
"The Government does seem persuaded of the need for more transparency and has given assurances to publish information where possible.
"However, this conversation will continue into the next parliament.
"JCNSS will not be rubber-stamping any Government responses until the Committee is satisfied we can meet our responsibilities to the public."