THE Scottish Government's defence of the council tax freeze as a vehicle for social justice has never been entirely convincing. True, ministers have produced figures showing that the less well off have saved more as a proportion of their income than the better off.

Yet there is no real doubt about who the big winners have been since bills were pegged at 2008 levels. People with the most expensive houses have saved thousands of pounds. Meanwhile the least well off, who do not pay council tax, have not saved a penny. Indeed, they have suffered more than most as councils have been forced to cut back on services they tend to rely on.

A survey conducted by the Commission on Local Tax Reform, the cross-party body examining alternatives to the council tax, rather gave the game away.

Overall, it found strong support for basing local taxation on people's incomes, which was seen by most people as fairer than the present property-based council tax.

But which group was least supportive of the idea? You've guessed it: those on higher incomes.

Analysing the survey, the commission found a "clear trend that households with higher incomes were less supportive of a tax based on income, and households with lower incomes were significantly more supportive".

In numbers, two thirds of people from the lowest income bracket strongly support an income-based local tax, compared with fewer than one in five of the highest earners.

Exactly the same trend emerges, by the way, when you look at people's council tax bands. The higher your council tax band, the less likely you are to support an income-based property tax.

The findings suggest the SNP would encounter significant resistance from the middle class voters it has courted so hard if it were to revive its idea of replacing council tax with a local income tax.

That's not a fight any party would relish. Add that to the list of problems which forced John Swinney to shelve local income tax in 2009 - his plan to cap the levy at 3p would have left councils £800million out of pocket, for one thing - and it's hard to see the SNP's election-winning pledge from 2007 ever being delivered.

That's perhaps why the commission is looking so closely at something rather different: a hybrid property-and-income tax.

In a report for the commission earlier this year, housing expert Professor Kenneth Gibb said a "property tax and supplementary income tax approach" could combine advantages from both system.

All the signs are, the commission will include such system in its range of options when it publishes its final report in the new few weeks. It might well appeal to the SNP as it retains at least of vestige of the party's original proposal.

A word of caution, though. In a report on local tax nearly a decade ago, former HBOS chief Sir Peter Burt argued strongly against multiple taxes, saying they would be costly and complex to operate and viewed by the public as a way of raising taxes.

A hybrid council tax might sound like an neat political compromise but that doesn't mean it would be an easy sell.