Federal government agencies are increasingly using exemptions such as national security to block information being released under freedom of information laws.
An auditor-general report released on Tuesday found the number of exemptions from FOI release being claimed by government entities had risen 68.4 per cent over the past five years.
The use of "certain operations" exemptions had more than tripled and "national security" exemption use was up 247 per cent.
The "certain operations" exemption covers requests for information about examinations or audits, the assessment of personnel and the "proper and efficient conduct of operations".
In total, 53,761 exemptions from FOI release have been claimed since 2011/12 for reasons ranging from personal privacy to law enforcement and business.
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About 10 per cent of requests a year are wholly refused.
Government departments and agencies receive about 31,000 FOI requests a year, with the immigration department the busiest.
The audit found 88 per cent of applications were being processed within the required 30 days.
Three departments specifically examined in the audit - attorney-general, social services and veterans' affairs - were found to have appropriately applied refusals and exemptions and conducted internal reviews.
"The administration of FOI applications ... was generally effective," the report found.
However there was "very limited quality assurance or verification of the reliability of FOI data" reported to the watchdog, the Office of Australian Information Commissioner.
The OAIC said in response it would put in place an FOI regulatory action policy.
