Green Party co-leader Russel Norman on Saturday compared Prime Minister John Key to the late Sir Robert Muldoon, saying he is divisive and corrosive.
In a speech at the party's annual conference in Christchurch, Dr Norman said the Government is rotten and is undermining democracy.
He told supporters the Government gives special favours to its friends and donors, and one example of that was the SkyCity deal to build a convention centre in Auckland.
Dr Norman said Mr Key is hostile to rational debate and intolerant of opposition and has become a corrosive figure in New Zealand politics.
He said Mr Key may not look like Sir Robert (a former National prime minister), but is acting like him.
Dr Norman said Sir Robert would recognise this Government as one after his own heart.
Earlier, Dr Norman said the grass-roots organisation of the party was in good shape.
He said the party showed it had a strong organisational base by collecting 240,000 signatures for a petition against partial asset sales.
PM hits back
The prime minister meanwhile has hit back at Dr Norman and the Green Party, accusing it of far-left, whacky policies.
But John Key said his Government is focused on the things that matter - like building a strong and stable economy with more, better paying jobs.
He said in a statement the Government is taking New Zealanders with it and is on track for moderate growth and a return to surplus.
Mr Key said the Greens threaten to drag New Zealand to the far left with wacky policies of printing more money and nationalising the electricity industry.