Australian Securities and Investments Commission chairman Greg Medcraft said he would “hunt down” whoever leaked information about the proposed bank levy to The Australian Financial Review ahead of the official budget announcement.
ASIC is investigating whether any abnormal trading in bank stocks took place on the back of information that was supposed to be highly confidential.
Australian Federal Police investigators are contributing to the probe.
“We will hunt this down as much as we can,” Mr Medcraft told budget estimates on Wednesday.
“I think everyone is concerned about finding out where the leak came from, frankly,” he said.
“It’s not good for Australia.”
Speculation the government would impose some form of new tax on the banks was aired on Sky News the night before the budget on May 9.
But it was veteran business journalist Tony Boyd who published more detailed information in the hours before the budget lock-up, Mr Medcraft said.
“I was concerned about the Tony Boyd article because it seemed quite well informed,” he said.
“It rang an alarm bell in me.”
The value of bank shares fell $14 billion prior to Treasurer Scott Morrison announcing on May 9 the $6.2 billion levy that will hit Australia’s big five banks.
ASIC’s market surveillance team noted changes in bank stocks on the morning of the budget but concluded that, at around 2 per cent, the fluctuation was not significant.
But the situation has since become clearer, Mr Medcraft said.
“Market integrity goes to the heart of the Australian market. If there is a problem we try to find it. Also I think we want to learn from it.”
Asked whether Treasurer Scott Morrison’s office is being investigated, ASIC commissioner Cathie Armour said the agency would speak with all relevant participants, including Treasury officials.
“Everyone who is in the circle will be relevant … everyone who had access to that information,” Mr Medcraft said.
On Monday, Treasury Secretary John Fraser said he would be “devastated” if the leak came from his department.