Told that four of the banks had produced estimates that suggested the levy would raise much less than the $6.2 billion forecast, Mr Fraser said the reporting of the estimates was too simple. Australia's major banks are fighting a levy announced as part of the Turnbull government's budget. Credit:Paul Rovere "Calculating what the tax will raise is very complex," he said. "You need to consider the timing of the payments and tax deductions and issues about bank credit and credit growth over time. We see no reason to step away from our forecast." Asked whether Treasury had modelled the impact of the impost, Mr Fraser replied that it had. "The results are what common sense would suggest: they are trivial," he told the committee. "Trivial with respect to interest rates," he added.

Mr Fraser sought advice from another Treasury officer sitting behind him, who described the impact as "negligible". John Fraser at Parliament House in Canberra on Monday. Credit:Andrew Meares Legislation to implement the levy is expected to be introduced this week. Asked whether he had personally pushed for the levy within the government ,Mr Fraser replied that the decision had been made by the government. Finance Minister Mathias Cormann closed down the line of questioning, saying it was inappropriate to ask the secretary for a personal opinion. Mr Fraser phoned the executives of the five major banks on budget night ahead of the budget speech to alert them to the levy.

He was aware of what appeared to have been a leak of the government's plan early in the afternoon. He was unable to calculate how much sharemarket trading had taken place as a result. The Securities and Investments Commission had referred the trading to the Federal Police. "I would be devastated if I thought that one of my staff had been responsible for this. I have seen nothing to suggest the leak came from within the Treasury," Mr Fraser said. "Can I give you a guarantee the leak didn't come from my department? No I cannot, but I would be devastated if it did. Treasury began an investigation into the apparent leak the morning after the budget. The department's chief operating officer, Peter Robinson, told the committee that knowledge of the planned levy had limited to fewer than 100 people. Mr Fraser said as a separate measure the security at future budget lockups would be tightened. Personal computers would be banned and there would be stricter checks for phones. "At the moment we rely on the honesty of people going into the lockup to surrender their mobile phones, and probably just as importantly, to put their laptops onto airplane mode," he said.

"It's sad to do this, and I hope I'm terribly wrong, but the ability for someone to say 'here's my phone' and neglect to say that they've got another one in their coat pocket or handbag is a bit of a worry." "We will issue everyone with Treasury iPads and people will be put their stories and reports onto USBs instead of using their own computers." The Treasury later put up a statement saying, while that was Mr Fraser's "preferred approach," the department and the Treasurer had not yet made a final decision.