Australian banks reaping huge profits from their New Zealand customers is a perennial scab that gets ripped off every time financial results come in.
This year the scab is extra nasty following the misdeeds, abuse and general appalling behaviour revealed by Australia's royal commission report into the sector.
On this side of the Tasman the Reserve Bank and Financial Markets Authority are due to release early next week their own conduct and culture review of local banks, although this is not nearly as wide-reaching or detailed as the Australian inquiry.
We've been told to expect comments about general areas of weakness across the industry rather than individual shortcomings being made public.
Meanwhile, Australia's big banks are starting to move away from vertical integration, partly because of conflicts of interest but also because their financial services model is unlikely to sustain the same profits over the longer term.
Suncorp, ANZ, CBA and NAB have all divested their life insurance operations. The latter two have also announced plans to spin off their wealth management operations. Westpac remains wedded to these areas of business but is expected to follow suit at some point.
And just last week financial services firm AMP, also heavily damaged by the banking royal commission, announced the sale of its wealth protection unit to US firm Resolution Life for A$3.3 billion and divulged plans to offload its New Zealand wealth management and advice businesses through a public offer and NZX listing next year.
All of this suggests the time is ripe to open up debate as to whether Australian banks should be required to have at least part of their core New Zealand banking businesses primarily listed on the NZX.
This is not a new idea.
Every few years a story appears in the media tipping one of the Aussie banks is considering spinning off and floating its New Zealand subsidiary, causing much salivation among investment bankers and local stockbrokers starved of new product.
The stories always turn out to be fake news, probably instigated by said brokers in thinking that if someone says it loudly enough it may eventually happen.
But if ever there was a time to raise the prospect of some form of domestic ownership and oversight of the banks, it is now.
The problem is it will never happen unless the Aussie banks are forced to by our politicians and regulators. After all, the last thing the banks want right now is another regulator to answer to.
They also claim loudly that any standalone New Zealand subsidiary would not have the same access to international capital and therefore would disadvantage consumers. Yet, why should it be accepted that four of this country's five most profitable companies are effectively regulated in Australia?
Although Australian banks, including ANZ and Westpac, have shares listed on the NZX, their primary listing is on the ASX.
Theoretically an Aussie bank could offload 25 per cent of the institution's New Zealand assets and list the shares here separately. That would bring tax advantages to New Zealand investors who can't use Australian franking credits, even though they are dual listed.
And, due to transfer pricing, Australian banks are currently able to minimise tax paid in New Zealand so the government could benefit from an increased tax take.
Last year New Zealand banks had their best year in more than three decades, according to KPMG's annual survey. Together, banks produced net profit after tax of $5.19 billion and judging by the latest results coming in, that figure will rise again this year.
These are four of the most profitable banks in the world and their most profitable geographical division is New Zealand. And yet because they are so dominant there's a degree of fear about doing anything to upset them.
It's a very bizarre situation.
If a quarter of these assets were listed that would bring about $12.5b of capital to the local stock exchange – a badly needed injection at a time when the main market is shrinking.
So what would it take to bring about such a move?
In spite of the noise the banks make about withdrawing credit from New Zealand under such a scenario, one suspects if they were forced into it, they would comply.
Yes they might fight tooth and nail to retain the status quo but New Zealand is simply far too profitable a market for them to reject.
And right now the Aussie banks are distracted with a battle on their home turf.
It's the perfect time for some Coalition politicians to show some backbone and make a case for a change in this direction.