Longo’s remarks come amid a record $5 million fine levied on the bank for failing to prevent these questionable orders, raising serious concerns about compliance and market integrity.

Macquarie showed a “poor attitude to compliance”, Longo told a parliamentary committee on Friday, stressing that the bank had not adequately responded to warnings about the involvement of three clients in those deals.

“What was particularly important, in my view, was not just the number of orders where this activity took place, or the fact that three Macquarie clients were involved, but how Macquarie dealt with the matter, the matter which, according to was my biggest concern,” Longo said.

“These warnings have been effectively ignored for far too long. There were acknowledgments, but no action. Macquarie failed to appreciate the seriousness of its obligations as a market participant.

Last month, following an investigation by the Australian Securities and Investments Commission (ASIC), the Markets Disciplinary Commission (MDP) fined Macquarie nearly $5 million for breaching market integrity rules.

The bank was found to have allowed three customers to make suspicious orders up to 50 times between January and September 2022. – a period marked by unprecedented volatility in global energy markets.

Each order exhibits characteristics of intent to "mark the close," affecting the daily settlement price in a way that benefits clients.

Commenting on the fine at the time, ASIC said the record penalty reflected Macquarie's serious and sustained failures to detect and prevent alleged manipulation of the ASX 24 energy derivatives market.

Also at the time, Longo revealed that ASIC had contacted Macquarie about these troubling orders on multiple occasions, claiming the bank had "repeatedly failed" to take timely action.

"The consequences of manipulating energy markets can have a detrimental effect on supplier financing costs and in turn on energy prices. This could lead to higher energy bills for consumers who are already struggling with the cost of living," the chairman said.

The MDP found that Macquarie's failure to address ASIC's concerns in the context of the increased need to monitor the electricity futures market was an aggravating factor in determining the amount of the penalty.

Expanding on that point on Friday, Longo noted that the fine not only marked the "highest penalty ever imposed" by the MDP, a panel made up of Macquarie's industry peers, but also served as a reminder of the seriousness of the situation.