The Maori and Mana Parties have hit out at Act's newspaper campaign, saying it is deeply offensive and calling leader Don Brash a dinosaur who has no place in politics.
Maori Party co-leader Tariana Turia said on Saturday that the campaign was deeply offensive, not in the interests of New Zealanders "and we will not be wasting our time in commenting further".
Last night, however, her co-leader Pita Sharples issued an open letter to Dr Brash.
"You once again bring the Maori people's aspirations into contempt and ridicule. Your views are not only inaccurate and ill-founded, but are totally out of tune with middle New Zealand's ideals and aspirations for our country.
"It is clear that since your exit from Parliament, you have learnt zilch about fostering an inclusive culture to take our nation forward," he said.
Mana Party leader Hone Harawira said in a statement addressed to Dr Brash: "Your attempts to boost Act in the polls by riding on the xenophobic fears of Joe Bloggs in the street will not work this time round.
"People can see your ad for what it is - a pathetic attempt to make people believe that Maori receive privileged rights and that the boot needs to be put into the indigenous people of this country so that rich people like yourself can feel better about themselves."
The ad ran in the Weekend Herald under the headline "Fed Up with Pandering to Maori Radicals?"
It explained why Act thought Maori were getting more rights than others.
The Dominion Post wanted to change the headline, Dr Brash said, but he wouldn't say what to.
The headline that ran in the Herald was a moderate version, Dr Brash admitted last night.
Creative director John Ansell had wanted to go "harder and further than I wanted to go".
Mr Ansell resigned his role on Saturday after posting comments on the Kiwiblog website suggesting the party was being cowardly.
"I don't want to associate myself with those comments at all," Dr Brash said.
Mr Ansell also wrote that Act's catchment was "men and women who think like men. Not men and women who think like women. Act is the party of the strong father, not the soft mother. (By strong father I include strong women like [Ayn] Rand, Richardson and Thatcher, and by soft mother I include weak men like Key.)"
Dr Brash took over the Act leadership in April.
When he was National leader, he boosted the party's polling after making the so-called Orewa speech in 2004 on a similar theme to the advertisement.
Act polled at 1.9 per cent in last month's Herald-DigiPoll survey and 1.7 per cent in last night's TV3 Reid poll.