New Zealand will lose another 400,000 people to Australia over the next 15 years, based on current projections of the income gap between the two countries, the 2025 taskforce says.

The taskforce, chaired by Don Brash, is charged with providing recommendations on how to close the income gap by 2025.

In its second report, released yesterday, it says OECD projections of each country's growth prospects would see the gap widen from 35 per cent to 42 per cent.

What should be done to close the pay gap between NZ and Australia?