Short-term fixes to the defence equipment crisis mean bigger costs in the long term, auditors have warned.

Reiterating the findings of the recent and highly critical review of defence procurement by Bernard Gray, the National Audit Office (NAO) has warned that value for money will be impossible unless underlying budgetary and governance issues are addressed.

NAO chief Amyas Morse said on Tuesday: "The Ministry of Defence (MoD) has a multi-billion-pound budgetary black hole which it is trying to fix with a 'save now, pay later' approach.

"This gives a misleadingly negative picture of how well some major projects in the MoD are managed, represents poor value for money, and heightens the risk that the equipment our armed forces require will not be available when it is needed or in the quantities promised.

"Bold action will be required to prioritise defence spending as part of the planned Strategic Defence Review after the general election."

Auditors have warned that, despite reducing planned expenditure by £15bn, the MoD still faces a shortfall estimated at anything between £6bn and £36bn.

The report has also warned that attempts to cut costs in the short term, by slowing work on projects, is contributing to the 'bow-wave' increase in costs further down the line.

The NAO, which examined 15 major defence projects as it does each year, has calculated that two thirds of the £1.2bn increase in costs during 2008/09 can be directly attributed to the slowing-down of projects.

For example, the report said, the decision to slow down work on the Queen Elizabeth class aircraft carriers will save £450m in the next four years, but add £1,124m in subsequent years - a net increase of £674m.