The Turnbull government has denied inequality is worsening in Australia and dismissed Bill Shorten's latest tax change push as the "politics of envy".

Treasurer Scott Morrison admits not all Australians are feeling the benefits of 26 years of uninterrupted economic growth but says the Opposition Leader's claim that inequality has reached a 75-year high is a "lie".

Mr Shorten is preparing to unveil new tax changes at Labor's NSW state conference this weekend - including a possible crackdown on family trusts and other forms of tax minimisation that benefit the wealthy - after declaring inequality to be the party's defining mission going into the next election.

"The current tax system isn't fair," Mr Shorten told reporters on Monday. "We've got a good record on tax reform and we will be outlining more tax reforms soon. Tackling inequality is a growth strategy."

But Mr Morrison said Mr Shorten had "given up on growth" and was instead fixated only on how to carve up the economy. 

The Treasurer warned people who use trusts - including farmers and small business owners - that Labor was "coming after you", and insisted inequality in Australia was getting better, not worse.

"This idea that people and inequality and incomes have been going in the wrong direction, that's not borne out by the facts," Mr Morrison said.

"The last census showed that on the global measure of inequality - which is the Gini coefficient, the accepted global measure of income inequality around the word - that figure shows that it hasn't got worse, inequality.

"It's actually got better."

The OECD's most recent economic survey of Australia, released in March this year, challenges the Treasurer's claim.

"The Gini coefficient has been drifting up and households in upper income brackets have benefited disproportionately from Australia's long period of economic growth," the paper found. 

"Real incomes for the top quintile of households grew by more than 40 per cent between 2004 and 2014 while those for the lowest quintile only grew by about 25 per cent. 

"Strong growth has pulled the incomes of households with wage earners further ahead of households reliant on transfers or pensions, which dominate the lower end of the income distribution."

Economist Saul Eslake also says inequality has increased in Australia but not by as much as it has in other advanced economies - partly because Australia has avoided recession and partly because it has a more progressive tax system.

The Gini coefficient is a number between 0 and 1 that represents a nation's equality, with 0 being perfect equality and 1 being total inequality.

In the early 1980s Australia's number was 0.2. It grew to 0.309 in 1995 and peaked at 0.334 in 2008/9 before falling in the wake of the global financial crisis, but the ABS has not published figures since the 2013-14 financial year.

Coalition MP Andrew Laming criticised Mr Shorten's "nasty egalitarianism" and said the government should be focused on alleviating poverty rather than inequality.

"Inequality is staring over the fence and noticing another guy has a jet ski and you don't have one," Dr Laming said.

But Dr Laming also conceded the Gini coefficient was beginning to rise again because the mining boom had ended.

NSW Liberal MP Craig Kelly said Mr Shorten was going down a dangerous road by preaching envy and class warfare and said it would "end in tears" by destroying incentives for people to create wealth.

Labor backbencher Peter Khalil said inequality in Australia was manifesting in wages, job security, education, healthcare and taxes.

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