WA’s auditor general says the failure of some Government agencies to properly disclose financial information could undermine public sector transparency and mislead the public.

Auditor General Colin Murphy has pored over the 2014-15 annual reports of 50 agencies, finding problems with 18.

The issues included failing to provide an audited version of their financial statements and key performance indicators (KPIs).

Others failed to include the coming year's financial estimates, which should be approved by their minister.

“Failure to include reliable information in an annual report undermines transparency and could mislead readers about an agency's performance,” Mr Murphy's report said.

Nine agencies’ financial statements or KPIs did not match those audited by Mr Murphy.

In one case, the Commissioner for Equal Opportunity incorrectly reported buying “non-current assets” as receipts for services.

In another, Corrective Services officers had their pay incorrectly reported, both overstated and understated.

The Department of Child Protection and Family Support “failed to disclose the ageing analysis of its financial assets”.

Agencies had a range of excuses for their errors; incorrectly changing figures after the audit, mistakes during the preparation of the annual report, or the accidental use of prior versions of data.

Eight agencies failed to properly report ministerially-approved financial estimates in annual reports.

“This is a concern as the annual report is the only place the estimates of these agencies are published as they are not included in the state budget papers,” Mr Murphy said.

But the agencies “overwhelmingly satisfied” a requirement not to include comments or information in annual reports that could be inconsistent with audited financial statements and KPIs.

Just two agencies committed what were deemed “minor errors” in this area.

The auditor general says most offices accepted the findings and were changing their annual reporting practices.