National Australia Bank has said that MLC, its wealth management unit, has the option to purchase a 23 per cent stake in financial planning firm Professional Investment Services, the Wall Street Journal reports.

The shares will be bought from Aviva PLC, the Australian bank reportedly said without providing details on the option terms. Industry talk reveals, however, that PIS could be worth at least $250 million.

NAB had taken over Aviva's Australian insurance business this year for A$285 million but had not taken interest in its PIS stake at the time. PIS has been struggling with a 20 per cent revenue drop since the financial crisis erupted last year and has resorted to selling its Canada-based start-up, although it decided to keep its Asian activities.

NAB said last week that it is working with PIS to explore future opportunities.

Whether or not these opportunities include an acquisition of PIS has yet to be confirmed.