Left leaning parties have opposed the expected appointment of former National leader Don Brash as head of a productivity taskforce.

Labour and the Greens today criticised the expected announcement that Brash, also a previous Reserve Bank governor, would chair a taskforce to work on ways to close the productivity gap between New Zealand and Australia.

ACT leader Rodney Hide said last month the Government had agreed to establish the taskforce, which was his party's policy.

The 2025 taskforce would aim to match Australia's productivity by that date.

Labour leader Phil Goff said the appointment showed a privatisation 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.

"You might have a smiling face at the front but behind that you've got the real face of what National party ideology is about."

He said the Government was promoting a privatisation agenda.

"We're seeing a set of Trojan horses set up by the National government aimed to achieve privatisation," he said.

"The comments that (Treasury secretary) John Whitehead has been making have not been made without permission and the support of the National Government."

Whitehead yesterday called for a shake-up of the public sector and more use of the private sector which has been taken as a call for privatisation and job cuts by some.

Goff said he believed comments NZX Ltd chief Mark Weldon made about privatisation of state owned enterprises were also government endorsed.

"It's all part of a plan that the National party has that's been ill-disguised and not denied by the prime minister."

Green Party leader Russel Norman said such appointments would dent the public's belief that National had become more moderate.

"The 2005 election was the defeat of the hard right within the National party. It's very worrying to see it reappearing again after we've had this very moderate face of the National Party."

The taskforce is to report by the end of the year, and annually after that, on what had to be done and its monitoring of progress.

Productivity would have to grow by about 3 per cent a year to close the gap, which at present is about 30 per cent.

New Zealand's productivity growth has been around 1 per cent for the last 10 years.