The government's spending watchdog has praised the OGC for negotiating Memoranda of Understanding on licensing costs, first with Microsoft and then Sun Microsystems, Lotus/IBM, Corel and Oracle.
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Some 31 government departments have used the MOU with Microsoft and five with other suppliers, producing £31m savings in 10 months, according to the OGC.
However, the NAO said many government departments and agencies had been slower than expected in taking up the new pricing deals.
Government organisations should also be "alert" to the price and other advantages as well as the risks of using a variety of software suppliers, the NAO added.
It also urged the OGC to step up its efforts to promote and monitor the use of the new pricing by departments.
The report said government bodies departments should maintain reliable information on expenditure on software and supporting licences and check at least twice a year to ensure no unlicensed software was being used.
It also said care must be taken to include the price of purchasing, licensing and upgrading software as well as of installation, retesting, problem solving and staff training in the initial estimate of the cost of a new IT system.
It warned: "If all these are not taken into account in purchasing decisions, the cost of the investment is likely to be understated."