A Whitehall team set up to cut IT costs in the public sector was requested to "ask more radical questions" about saving money by government IT leaders, documents released by the Cabinet Office reveal.

The review team – set up last July – is led by former Logica chief executive Martin Read, and known as the Operational Efficiency Programme (OEP).

The Treasury's pre-Budget report announced last November that "additional value for money savings have been identified through the work of the OEP including through collaborative procurement and back-office efficiencies."

But in a session just two months before the announcement, and some three months after Read's review began, members of the Chief Technology Officer (CTO) Council were briefed that the Chief Information Officer (CIO) Council had " asked the review team to ask more radical questions about challenging costs" at a recent meeting, according to Cabinet Office minutes.

The previous meeting of the CIO Council took place on 24 September and had the OEP as the second item on its agenda.

The exchange of views between the review team and the CIO Council will raise questions about whether the programme has had time to identify the full range of savings available by next month, when it will publish its findings as part of Alistair Darling's Budget.

Last month Read told the Government IT conference that total annual government spending on IT could be anywhere between £13bn and £21bn – the sprawling nature of the public sector made it impossible to tell.

Read and his team used five different methods to evaluate public sector IT spend, and came up with results as low as £13bn and as high as £21bn, finally settling on an average figure of about £16bn in 2007/08, though he admitted it was a "very inexact science".

Read said he had identified "substantial" savings which would be announced alongside the Budget.

The Cabinet Office said the CIO Council's informal meeting with members of Read's team was part of his initial gathering of facts and evidence.

"The CIOs assisted the review by sharing their experience of radical challenge of specific cost drivers (such as desktop and network) as well as using overall aggregates and international comparisons," said a spokesman.