Known as PIEs, the loophole allows top rate taxpayers to be taxed on their savings at 30% rather than 39%.
For someone with $100,000 on deposit, the saving is $15 a week, much more than the 67c a week 'chewing gum' taxcut, cancelled by Mr Cullen in his budget of 2007.
Stuff explains how the policy operates here.
But isn't it just one of the many ironies from what is supposedly the worker's party- a tax break for the rich.
Of course, it just adds to the continuing tax relief for investment properties making Liarbour the Landlords Party, rather than that of homeowners or tenants.
But I guess this is what happens when you have a long in the tooth government who takes its constituency for granted.