ANZ is calling for a change to KiwiSaver rules to avert what it calls a $72,000 hole in the value of many individual retirement accounts.
The bank is blaming this problem on the way the KiwiSaver default scheme works.
Under KiwiSaver rules, people who do not specify where their savings should be put are enrolled automatically into so-called conservative schemes with low growth rates but also low risk.
ANZ says an estimated 190,000 people are getting far less in their accounts than they could - which it calls a ticking time bomb.
The bank says the problem could be averted if the default system channels people into high growth schemes when they are young and progressively move them to conservative schemes as they get older. This could add $14 billion to total retirement savings, it believes.
John Body, ANZ's managing director of wealth, says younger people should be put on higher risk investment schemes as a default with the opportunity to opt out.
"How does a 25-year-old with $1000 in KiwiSaver get access to advice around where they should invest.
"Our view is, we should start off with people in an option that suits their time profile and then they can default back into other profiles if they're more suitable.
"But let's try and get as many people in the right bucket, if you like, first."