Self-professed union whistleblower Kathy Jackson used $1 million in members' funds to pay off two personal credit cards she claims to have used on work expenses between 2000 and 2011, despite having a union credit card.

Fairfax Media can also reveal documents provided to the Health Services Union by the Commonwealth Bank in the past few weeks show that between 2007 and 2010, Ms Jackson withdrew a further $220,000 of union funds in ''cash'' using HSU cheques.

Card use: Kathy Jackson used $1 million in members' funds to pay off two personal credit cards, Fairfax Media can reveal.

The HSU is preparing to provide the documents to the union regulator, the Fair Work Commission, or the royal commission into union corruption, and request they be scrutinised to determine whether Ms Jackson's expenditure was reasonable and subject to appropriate accounting standards.

''The amount of union funds that were spent by Ms Jackson ostensibly for work practices is staggering. We don't know for certain how most of the money was used, but there appears to have been no checks and balances in place to ensure it was used in a way the members wanted,'' a senior union source said.