The South Australian branch secretary of the Australian Education Union Leah York has quit amid shoplifting allegations.
The AEU said Ms York had resigned following "an incident in Mt Gambier last week".
Her decision comes after a local store posted videos online of a woman appearing to place an item in a shopping bag before leaving the store.
In a second video, the store said the woman had rung to pay for a handbag but a further review of CCTV footage had also revealed a second item had been taken.
The store said the incidents were "not fair to local businesses going about their daily grind".
Police are investigating the allegations.
In a statement on Thursday, the AEU said it was in the process of determining interim arrangements to fill the branch secretary position.
"An election to fill the casual vacancy will be held and conducted by the AEC following regular Registered Organisation Commission processes," the statement said.
"The interests of AEU members remain our focus during this time."
Ms York's decision to quit the union comes after she also resigned on Wednesday as a board member of Funds SA, the investment manager for public sector superannuation.
She had been appointed to the Funds SA board in 2018.
In a statement to the Adelaide Advertiser, Ms York described the incident in Mt Gambier as a misunderstanding.
