"It was and has been a more painful adaptation than we thought, and not in line with what we have seen in South Australia, Tasmania, UK, France, South Africa," he said.
"So it was painful, our experience in our pilot stores is that it takes about eight to ten weeks for customers to adapt to the new world, and we're starting to see that happening."
Mr. Banducci said that customers put less stuff in their basket if they forget to bring a bag to do their shopping. The supermarket has added more staff to the checkout to take into account the longer packaging mines caused by customers taking non-standard sized bags.
He also claimed that disposing of disposable bags was a profitable exercise, with the time lost at the checkout offsetting the income from the sale of reusable bags.
Sales in Australian supermarkets grew by 4.3% in 2018, but slowed to 3.1% in the fourth quarter and to 1.3% in the first seven weeks of the new fiscal year.
The problem was aggravated by Coles' Little Shop toy giveaway, which Mr Banducci acknowledged was a success for his rival, while Woolworths had no competitive offer.
This quarter the trade is considerable for Coles, as it will be the last to be released before the owner Wesfarmers will play it in November as a separate listed company.
Coles recorded the strongest sales growth last week in almost two years, but said that the bag ban has not made any significant difference in its performance.
Bags for single use are now banned in supermarkets in Queensland, Western Australia, South Australia, Tasmania, ACT and NT. Victoria intends to ban them by the end of 2019, and leaves NSW as the only state or territory not to act on this issue.