A parliamentary inquiry threatened to hold Brad Banducci, the chief executive of Woolworths, in contempt during a fiery hearing as Australia’s big supermarket chains faced claims they price gouge shoppers and coerce suppliers.

Banducci was asked by the Senate committee on Tuesday to disclose the company’s return on equity (ROE), an important gauge of profitability, amid a discussion over whether its profit levels were reasonable in a cost-of-living crisis.

Banducci repeatedly declined to answer the question, preferring to cite a different profit metric that was lower and that he argued was more relevant.

• Sign up for Guardian Australia’s free morning and afternoon email newsletters for your daily news roundup

The Greens senator Nick McKim, who chairs the Senate committee into supermarket practices, warned Banducci that he may be found in contempt, which he said carries a penalty of up to six months’ imprisonment.

McKim said Banducci was engaging in spin, “cherrypicking” facts and “bullshitting the committee”.

“I put it to you the reason you don’t want to focus on return on equity is because you don’t like the story that it’s telling, which is that you are basically profiteering and making off with massive profits at the expense of farmers, at the expense of your workers and at the expense of Australian shoppers, who you are price gouging,” McKim said.

“Why won’t you answer a simple question about what your ROE is?

“Are you struggling with the ordinary English language meaning of the words that I’m using in my questions?”

Banducci said it was not a relevant profit gauge for Woolworths. “With respect, we look at return on investment,” Banducci said, referring to a measure of investment efficiency.

“I’m focusing on corporate finance, senator, and that’s what we use.”

Banducci told the committee Australians wouldn’t shop at Woolworths if it price gouged.

“If we do not generate value for our customers, they don’t shop with us for the whole or part of their basket,” Banducci said.

Banducci was counselled by other committee members to be more cooperative.

“I’m here to be constructive and to be helpful because we have important issues before us on the cost of living of Australians,” he said. “I have been authentic and clear in answering the question that as we assess profitability in our sector I look at return on investment and total shareholder returns.”

McKim, who accused Woolworths of “making off like bandits” with a “licence to print money”, told Banducci that the Senate could hold a witness in contempt if they refuse to answer legitimate questions.

“I also feel compelled to advise you that that opens up a range of sanctions, personal sanctions that can be applied against you if that’s what the Senate decides to do.”

The standoff escalated to a point where the hearing was temporarily suspended.

Banducci then appeared to concede he did not know what the ROE figure was for the most recent financial year, prompting the committee to allow him to take the question on notice.

The inquiry is designed to investigate how big supermarkets set prices for shoppers and use their market power when dealing with suppliers. Coles and Woolworths collectively control two-thirds of the market.

There has also been a sharp focus on the strong profits recorded by Coles and Woolworths during a period of fast-rising grocery prices.

Food consumption data shows that households have been buying less food, especially fruit and vegetables, as prices rise. The slump in demand, however, has not dented supermarket profit making as it typically would in a more competitive market.

The Coles chief executive, Leah Weckert, avoided a confrontation with the Senate committee by disclosing the company’s relevant profit metric at the start of her questioning on Tuesday.

Coles was taken to task, however, for not providing details to the committee on product profit margins and sales figures, which Weckert said was commercially sensitive data.

She said Coles would provide the data to a separate inquiry by the competition regulator, if requested, because of confidentiality measures that are in place.

Weckert acknowledged the supermarket company needed to improve how it interacts with produce suppliers, amid claims the major chains unfairly use their market power when negotiating prices.

“We acknowledge that we don’t always get it right, but all our procedures seek to ensure fair and sustainable relationships,” she said.

The inquiry has heard that many suppliers fear raising concerns with Coles and Woolworths because of their market dominance.

Fresh produce producers and the dairy sector have told the committee that their sectors are at threat due in part to what they describe as unsustainable pricing demands.

Coles representatives have offered to meet with any concerned suppliers and invited Senate committee members to attend.

• Woolworths
• Coles
• Business
• Australian politics
• news