Former treasury secretary Ken Henry and author of a landmark tax review a decade ago believes the tax system has "gotten worse".

He said when he handed down his review to the then Labor government under Kevin Rudd, he believed it would take a decade for all its measures to be introduced.

"I am today absolutely stunned that so little has actually been implemented," Dr Henry told ABC radio on Friday.

"It is costing Australia quite a lot."

But Senator Cormann says his government has pursued the "most significant reform" to the personal income tax system since the early 1990s.

He said under the government's legislated tax reforms, 94 per cent of Australians will not pay more than 30 per cent tax on any of their income.

"We have got rid of an entire tax bracket," he told Sky News.

"We have obviously also made various other adjustments which not only deal with bracket creep but also simplify the tax system moving forward."

He said the government is always reviewing what can sensibly be done, particularly in the lead-up to every budget and mid-year budget update.

But Dr Henry argues that Australians are going to lose out "really big time" if there is no tax reform.

"They are going to find government incapable of financing their needs," he said.

"These tax systems, both at the commonwealth and state level, are simply unsustainable."

The take-out by Labor from the Henry tax review was a mining tax, or the minerals resource rent tax, which was scrapped by the coalition under Tony Abbott when it came to power in 2013.

An analysis by the Organisation for Economic Cooperation and Development on Thursday showed that while Australia is taxed relatively lightly as a nation, it does rely heavily on corporate and personal income taxation.

Australian Associated Press