Pyne Gould Corporation's subsidiary, Perpetual, says it's in advanced talks with ASB about buying the bank's investment management business, Aegis.
The electronic administration service holds, trades and reports on investments and has more than $5 billion in funds under administration.
Pyne Gould Corporation chief executive Jeff Greenslade says Perpetual has been a customer of Aegis since 2003 and developing the business further would support its long-term wealth management strategy.
No price has been given, but Mr Greenslade says an update on the possible purchase will be made by the end of the month.
Pyne Gould's finance arm Marac is currently in talks with Canterbury Building Society and Southern Cross Building Society to form a $2.2 billion 'Heartland' bank.