ASIC quick to move on potential levy leak

The securities watchdog independently launched an investigation into a potential leak of the Turnbull government' s proposed bank levy before it was asked.

Officials at the Australian Securities and Investment's Commission became suspicious of a potential leak when they were aware of news articles before the levy was announced in the May 9 budget and the price action in shares on the day.

"We launched an action before anyone asked us about it, we were already on the job," ASIC chairman Greg Medcraft told a Senate hearing on Wednesday.

"We think this is quite important to market integrity."

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.

The Australian Federal Police is also investigating a potential leak.