Almost one thousand elective surgeries were left off Victorian waiting lists, with an audit now under way to discover if it was a case of deliberate data manipulation.
Some 943 patients across 11 health services have been kept off elective surgery waiting lists since 2011 because their procedures were classified with the wrong code.
Victorian Health Minister Jill Hennessy has ordered an immediate independent audit of all health services to check for evidence of any deliberate data manipulation.
"I expect that patients waiting for surgery are assessed and wait-listed according to clinical need," Ms Hennessy said in a statement on Friday.
"What has occurred is inexcusable and I extend my deepest apologies to all those affected.
"We've taken immediate action to fix this situation and make sure affected patients get the clinical attention, surgery and care they need."
Monash Health recently found a number of patients waiting for "low urgency" procedures like breast reductions and tummy tucks were incorrectly classified so they weren't on the list.
These patients will now all be offered a clinical appointment within three months and, if confirmed to be appropriate for surgery, will be added to the publicly reported waiting lists using the appropriate code.
"The reporting process that allowed this error to occur has been abolished and Victorians can have confidence we're putting in place measures to ensure this never happens again," Ms Hennessy said on Friday.
The minister said if there was any evidence of intentional wrongdoing the matter would immediately be referred to Victoria Police and the Independent Broad-based Anti-Corruption Commission.