Barry Soper: Will today's report be the coalition's biggest challenge yet?

Winston Peters has previously flagged a lack of support for a capital gains tax.

COMMENT: Today's delivery of the Taxation Working Group's report will present this coalition with its biggest challenge yet.

The report's expected to recommend a capital gains tax which was last advocated by Labour during the 2011 election campaign - and the then-leader David Cunliffe got the message loud and clear from the electorate at the ballot box.

The election next year could potentially be history repeating itself.

Labour says any changes to the tax system will be legislated before the election and introduced after it. So the election will effectively become a taxation referendum.

Electoral history is on Labour's side, the last time there was a one-term government was following the death of Labour Prime Minister Norman Kirk in 1974.

The last truly reformist government was the late David Lange's, who let Roger Douglas loose in 1984. But the public bought the line, short-term pain for long-term gain, and it hurt.

But then it had to, the country was emerging from the clenched fist of Muldoonism, who had operated an icebox economy, freezing everything from mortgage interest rates to prices. So the country was facing a crisis and the electorate was prepared to suffer the first three years and gave Labour the tick for another three when it was implored to let it finish the business.

This Government faces no such crisis. They were presented with a healthy balance sheet and they're raking in around $80 billion in tax each year. If as Labour says, any tax changes are going to be fiscally neutral, you'd have to ask why change it?

But to change it, Labour will have to get the tick-off from its support partners.

The Greens will go along with it but the grumpy Winston Peters has in the past expressed his opposition to taxing capital gains. This week he's said there's already a capital gains tax and of course he's right. The bright-line test taxes the increased value of property if it's flicked on within five years of purchase. Under the last government it was two years.

So if the working group's recommendations go down like a lead balloon, and if New Zealand First stops them, it's not going to do them any electoral harm.

And it won't have done the bank balances of those who worked on the taxation group any harm either with the chairman, Sir Michael Cullen, picking up more than a grand a day while his 10 co-workers raked in $800 for each day's toil.