Flagging a worse-than-expected result in the mid-year budget review to be released next week, Mr Hockey said he had to “write down a hell of a lot of revenue” as a result of a slump in the iron ore price.

“Since I delivered the Budget in May, we have seen iron ore prices drop by nearly 40 per cent, which is extraordinary,” Mr Hockey said yesterday.

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“Now, iron ore is one-fifth of Australia’s exports and the price to drop nearly 40 per cent in the last few months has meant that the Government’s revenues have fallen again.”

The Treasurer said his Budget had taken a further hit from spending on an upgrade to the computer system used by Centrelink and Medicare.

Warning that the IT overhaul had cost “a lot of money”, Mr Hockey said there were still delays for people trying to get information about their welfare payments or Medicare rebates.

“It takes 17 minutes on average for Centrelink to answer a phone call, despite their best endeavours,” he said.

“When we were last in Government it was seven minutes.”

The warnings suggest a worse-than-expected Budget position will be revealed when the Government releases its Mid-Year Economic and Fiscal Outlook next week.

Treasurer Joe Hockey (right) says he wants bipartisan support for the Government’s response to the review of Australia’s financial system by David Murray (left). Source: News Corp Australia

Declaring voters were “over the combat of politics and want to see some co-operation”, Mr Hockey urged the Opposition to back his proposals.

He said he wanted bipartisan support for the Government’s response to the review of Australia’s financial system conducted by former Commonwealth Bank boss David Murray.

But Mr Hockey insisted not all of the proposals in Mr Murray’s report would be Government policy. The report includes politically risky suggestions for a crackdown on perks for property investors, including negative gearing and capital gains tax concessions.

It also calls for a major overhaul of superannuation, including changes to tax and for pension-style payments upon retirement instead of lump sums.

Mr Murray said he was not able to make specific recommendations about tax changes, but pointed out problem areas that the Government should look at it before the next election in its tax white paper.

Warning that housing was a “systemic risk”, Mr Murray said tax incentives and Australia’s love affair with home ownership was driving up prices.

“The apparent safety of housing from a lender’s perspective and the apparent security from an owner’s perspective leads people to speculate quite heavily in housing versus other assets,” he said. “If there are incentives in the system to do that over other investments, that can exacerbate the problem.”