Former National leader Don Brash says nothing is off the table after being tasked with finding answers to New Zealand's growing wage gap with Australia.

Dr Brash was named yesterday as head of a $477,000 task force set up to boost productivity but his appointment has sparked alarm among the Opposition, which fears he will advance a radical Right-wing agenda.

"[Dr Brash] has been very frank about his support for privatisation and a Right-wing ideology to govern the direction this country moves in," Labour leader Phil Goff said.

Finance Minister Bill English, who was rolled by Dr Brash for the National Party leadership, said it was "a very positive appointment".

Dr Brash said there were no limits on what the task force should consider and it would act as "a fresh pair of eyes".

New Zealand's national productivity the amount we produce per hour of work is lagging behind that of most other countries, despite our working longer hours than workers in most other developed countries.

Dr Brash said telling people to work harder was "absolutely not the answer". "It's not that we're under-working; one of the things that appears to be the case is we have less capital, less plant and machinery, less infrastructure per worker here than in Australia or other developed countries."

The reasons for that were varied, but included tax, savings behaviour, government spending and the Resource Management Act.