Images have emerged on social media of Wodonga-based Senator Bridget McKenzie inside a Bunnings store without a mask.
The pictures show Senator McKenzie standing in line at the checkout at what is believed to be the Wodonga store next to a man also without a mask, but behind two other people who are wearing masks.
They were posted to Twitter on Tuesday night.
Mask rules in Victoria were relaxed this week, but people are still required to wear them in bigger retail stores such as Bunnings and where they cannot socially distance.
Senator McKenzie told The Border Mail that she believed she was following the Victorian government's requirements that masks were "no longer be mandatory in all public indoor settings".
"As required, I left home with a mask and visited several local shops large and small, including Wodonga Bunnings," she said.
"At no point during the day was I asked to put my mask on by retail staff.
"Subsequently I sought clarification in regard to the regulations."
She said COVID-19 was a challenge people have to learn to live with by following medical advice and behaving in a COVID-safe manner.
"My office implemented strict COVID-19 guidelines to remain open throughout these difficult and confusing times to assist our border community," Senator McKenzie said.
"Our entire border community has taken our responsibility in this crisis very seriously despite the severe challenges we face."
A statement from Bunnings on its website says "the wearing of fitted face masks is now a condition of entry to all our Victorian stores, unless you are exempt".