Disgraced former unionist Kathy Jackson is now facing more than 160 criminal theft and fraud charges for allegedly misappropriating hundreds of thousands of dollars from the Health Services Union.

Ms Jackson appeared on Monday morning in the Melbourne Magistrates Court, where she faces the prospect of criminal convictions and a jail sentence if she is found guilty.

Police allege Ms Jackson misrepresented more than $500,000 of personal expenses as union expenses while she was the HSU secretary. All 164 police charges relate to 70 allegations that were laid against her by detectives from Taskforce Heracles last year.

Racked up on her multiple union-issued credit cards, her allegedly illegal expenses include hundreds of thousands of dollars on airfares and luxury hotel accommodation while Ms Jackson was on multiple overseas vacations in cities such as New York, Las Vegas and Hong Kong.