"AMP Capital will be considering how best to deliver our New Zealand equity management to our clients," the letter says. "Once the review is complete, we will be consulting with all of our clients and related parties."
The well-respected Guy Elliffe, head of NZ equities, and Jonathan Davis, senior analyst, will manage the approximately $1 billion portfolio until the review is finalised.
It is understood, AMP Capital has lost a few NZ equities clients of late following a period of indifferent performance and concerns about staff turnover.
According to the latest NZ fund manager investment survey published by actuarial firm Melville Jessup Weaver (MJW), AMP was ranked 11th out of 18 Australasian equity managers by performance over the last year and 11th out of 12 for the three years to September 30.
As well as managing money for a range of external wholesale clients, including the New Zealand Superannuation Fund, AMP Capital also runs NZ equities for associated entities such as the group's KiwiSaver scheme.
Mark Weaver, MJW chief, said Lau's resignation should give AMP a good opportunity to "get its shop in order, and build for the future".
An AMP spokesperson said Lau's exact departure date has yet to be determined.