BT Financial Group's four-year, $500 million investment in its wealth management platform has given it the ammunition it needs to dominate the fiercely contested $888 billion investment platform market, says its chief executive.

Westpac's wealth arm BT said it would take a $70 million revenue hit after unveiling lower fees and a streamlining of its superannuation offering at a time when fees charged to manage retirement funds have come under intense scrutiny amid outrage over evidence emerging from the Hayne royal commission.