Federal politicians and their spouses are using family trusts more than any parliament before them, and at 10 times the rate of ordinary Australians.

Trusts are growing fast in popularity, particularly among wealthier Australians as a way of minimising tax, and are now estimated to cost government coffers up to $2 billion in lost taxes every year.

However, the issue has not been raised as part of the current tax debate.

"It's not surprising they (the MPs) are reluctant about reform and legislating to rein in trusts," said business author and former tax officer Rod Caldwell.

"You're asking them to legislate against their own hip pocket interests."

A Fairfax Media analysis has identified that almost half (47 per cent) of Coalition MPs or their immediate families have an interest in trusts, a proportion considerably higher than previous parliaments and much greater than in the wider population.

Of the 105 Coalition MPs, 49 have a personal or family interest in a discretionary trust, while active involvement in family trusts is closer to 5 per cent in the general population.

Among senior members of the government, the proportion is greater still, with half - 10 out of 20 - of cabinet with trusts. This includes foreign minister Julie Bishop, employment minister Michaelia Cash and immigration minister Peter Dutton, as well as key economic portfolio holders Scott Morrison and Kelly O'Dwyer.

Labor MPs are much less trust-inclined, though the proportion of Labor MPs with trusts is growing. About 21 MPs or families in the current ALP caucus (22 per cent) now have trusts. This includes deputy leader Tanya Plibersek, shadow attorney general Mark Dreyfus and fellow Victorians, David Feeney and Tim Watts.

South Australian senator Nick Xenophon is a prominent crossbencher with a trust, and Victorian senator Derryn Hinch also have them.

Senator Nick Xenophon has a family trust. Photo: Andrew Meares

Neither Prime Minister Turnbull nor Opposition leader Bill Shorten has a family trust.

On Friday, Prime Minister Malcolm Turnbull stressed he did not have a family trust and that he had "always been very conservative" in his approach to tax. But he confirmed there were no plans for "sweeping changes" on taxing trusts.

"Trusts are a very legitimate form of business structure," he told 3AW's Neil Mitchell. "They're very widely used in small businesses, in family business, particularly with farms."

The popularity of trusts among MPs compared to the general population is consistent with the observation that they disproportionately benefit wealthier Australians - particularly those on incomes of $500,000 or more - at the expense of average taxpayers.

Serious reform of the tax advantages of trusts has not been proposed since Howard-era treasurer Peter Costello was stymied in his attempts by his Coalition colleagues in the early 2000s.

University of NSW trust tax law expert Dale Boccabella estimates that trust tax perks are costing government coffers $2 billion a year or more, a bill picked up by other taxpayers.

Even though the Coalition lost 17 seats at the July 2016 election, the number of its MPs with trusts has risen, up from 43 in previous parliament, and from 35 in the Gillard/Rudd years when Labor ran a minority government.

And where records or reports are available, they point to far fewer MPs in the past with trusts, especially in Labor-dominated parliaments.

Trust use is also increasing in the wider community.

Unpublished figures provided exclusively to Fairfax Media by the Australian Taxation Office reveal almost 643,000 discretionary trusts (most family trusts are this kind) in Australia in the 2014-15 financial year (the most recent figures), about twice the number of 20 years earlier.

Despite the growth, only about 5 per cent of the nation's 13.4 million taxpayers have discretionary trusts, a fraction of the equivalent percentage for Coalition MPs.

Peter Dutton has a family trust. Photo: Alex Ellinghausen

Another 13 government MPs have self-managed superannuation funds (SMSFs) or other investment vehicles.

Lack of transparency is an issue with both trusts and SMSFs. While MPs are required to declare family trusts and super funds along with companies and shareholdings, they are not obliged to declare investments made by trusts or SMSFs.

It is possible, therefore, for a resources minister to have large shareholding in a mining company, through a trust or SMSF, but not declare it.

Tanya Plibersek has a family trust. Photo: Wayne Taylor

This week Transparency International called on the government for greater scrutiny of trusts, including a national public register. When told of the Coalition interest in trusts, Transparency chief executive Serena Lillywhite said: "This may explain why it's taken so long for a regime to be developed to clamp down on the use of trusts and shell companies".

Trusts are a legal means of handling personal, business and family finances, and Australia has many forms of them, some of which are devoted to looking after people with disabilities, and children.

But the vast majority of discretionary trusts, in particular, appear to have no purpose other than to minimise tax.

This week Fairfax Media sought comment from Mr Turnbull and most of the Coalition MPs with trusts. Only two MPs responded, both backbenchers. Neither Mr Turnbull nor Mr Morrison responded. The usually forthright Senator Xenophon also failed to respond.

• An earlier version of this story wrongly reported that independent MP Andrew Wilkie had a family trust. He no longer is involved in a trust.