Joe Hockey’s latest thought bubble on tax cuts could have come from the Readers’ Digest, Opposition Leader Bill Shorten says.

The Treasurer has flagged the government will be taking the promise of personal tax cuts to next year’s election, but has yet to say how they will be funded.

Mr Shorten said Mr Hockey needs to explain how tax cuts are possible.

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“You just can’t help but wonder, did he get half way through a Readers’ Digest article on income tax cuts on an aeroplane trip somewhere and say, `that’s something I’ll talk about to the national media’,” Mr Shorten told reporters in Brisbane.

He said the government has no plan for tax reform, other than to extend the GST to fresh food, school fees and health care costs.

But Finance Minister Mathias Cormann insists personal income tax cuts will be part of a broader tax reform package.

Mr Hockey said last week tax cuts were needed to offset bracket creep, which over the next few years will force thousands of average earners into a higher tax bracket just through wage inflation.

“That is our objective to take to the next election a tax reform package … if you reduce revenue you need to make that up from other sources,” Senator Cormann told Sky News.