Serving as Chair of the Select Committee on Supermarket Prices, Mr McKim led a multi-hour interrogation of the CEO as part of an inquiry into price gouging.

The former Tasmanian Greens leader repeatedly asked Mr Banducci what his corporation's return on equity was, only for the CEO to refer to Woolworths' return on investment.

Speaking to media during the committee's lunch break, Mr McKim said Mr Banducci had "insulted the Senate and by extension, the Australian people".

"Part of the problem with the way Australians feel about their major supermarket corporations is a lack of transparency," he said.

"That was on full display today when the CEO of Woolworths just refused to answer simple and obvious questions that were put to him by the committee."

Mr McKim said both Coles and Woolworths were boasting "obscenely large" profits each quarter, while countless Australians struggled to put food on the table.

"It is extraordinary that someone on a multi-million dollar annual salary, who has been paid over $65 million since they became the CEO of Woolworths, doesn't know what the return on equity of his corporation is," he said.

"Nothing that Coles and Woolworths have brought to the table today rebuts the central allegation of price gouging."

The Senator garnered particular attention for threatening Mr Banducci with jail time on the grounds of his contempt of the committee.

Mr McKim later clarified that failure to comply with an order is able to be taken as a contempt of the Senate.

"The Greens make no apologies for holding the CEOs of giant corporations to account," he said.

"If that includes threatening them with jail time for not answering simple questions at Senate committee inquiries, so be it."

Fellow committee member Tammy Tyrrell brought questions from her constituents to the meeting, but Mr Banducci was unable to answer them in detail.

Having been elected through the Jacqui Lambie Network in 2022, Ms Tyrrell resigned from the party in March and went independent.

As the only other Tasmanian Senator on the six-member committee, Ms Tyrrell said she wanted to give residents "a seat at the table".

"Tasmanians just want to know why it seems like prices go up every time they go to the supermarket," she said.

"I know what it's like to grow up in a family that can't afford to buy groceries for three meals a day. These are the people that I'm giving a voice to at this inquiry."