The census has been saved and the Australian Bureau of Statistics will get a $250 million funding boost as part of the biggest technology upgrade in its 110-year history.

The five-year grant, which will be included in next week's federal budget, will be used to replace computer systems that are up to 30 years old, some of which fail to perform properly weekly and daily.

The government's expenditure review committee was told the bureau had 500 separate computer systems. One in three were unreliable and one in six were so outdated they were no longer supported by their vendors.

The bureau proposed releasing it from the obligation to conduct next year's census as a way of funding the upgrade but the budget committee rejected the request after sounding out Labor. The Census and Statistics Act requires the bureau to conduct the census every five years and ny change to that Act would have needed support in the Senate that Labor was unwilling to guarantee.