Ken Henry believes tax changes have a better chance of success if there is a broader community understanding about the needs and the problems they aim to fix.
Dr Henry, the former treasury secretary and architect of the Henry tax review, told a forum in Canberra on Monday that what was eventually legislated and implemented was almost always a long way from what was initially proposed.
"The question it raises is one that I dare not ask really, which is whether it is worth bothering at all," he told the Australian National University forum which is examining his review.
Asked for his thoughts on the federal government's minerals resource rent tax (MRRT), Dr Henry replied, "Obviously I won't say everything I think about it."
The 30 per cent MRRT was no simpler than the initially proposed 40 per cent resource super profits tax, he said.
"There is no way the public can understand what has been legislated ... it's actually more complicated than was originally proposed."
The GST and tax-free elements of superannuation were exempt from discussion in the "root and branch" Henry review released two years ago.
However, since then many economists and academics have called for the GST base to be expanded or the rate increased, or both.
Dr Henry said he was pleased to see the discussion occurring, given the challenges to the economy-wide revenue base in the years ahead because of an ageing population.
Former federal Liberal leader John Hewson told the forum the GST that was introduced by the Howard government in 2000 was compromised by politics and ended up being a very expensive and complicated system that did not achieve a lot of its objectives.
John Freebairn, a professor of economics at the University of Melbourne, said broadening the GST would result in greater efficiencies and simplicity and would allow income tax to be reduced.
But he noted that the main political parties were saying no to changing the GST.
"That to me says that this must be a bloody great idea," he told the forum.