Peter Gershon, who has advised the government on efficiency savings in the past, has told the Conservative Party it could save between £2bn and £4bn by stopping any new major spend on IT.
The Tories want to make an additional £12bn of savings, on top of the £15bn the government is already planning.
Gershon was commissioned by the government in 2003 to investigate how the public sector could save money by cutting back office costs and getting better value.
He said in an interview with the Financial Times that stopping major new spending and cancelling poorly performing projects could save billions, although cancellation fees might eat up the first year's savings.
Gershon said the public sector could make further savings by getting a better deal out of current contracts and suppliers.
A range of other reports, including one by ex-Logica chief Martin Read, have also identified ways to save money.