Green Party co-leader Russel Norman says he does not want appearances to detract from the party's message.
At the party's annual meeting in Christchurch, which ended on Monday, Dr Norman was the only person in a suit and tie.
That, he says, is an intentional move to a more professional image.
He says it is really important that he is able to communicate what he thinks are critical messages for the country, without anything getting in the way of that.
Clean green brand 'undermined'
In his keynote speech to the meeting, Dr Norman said that New Zealand's "clean green" brand is being undermined.
He told about 200 party members that both the current and former governments have failed to protect the environment.
When Labour was in office, Dr Norman said, it took advantage of the brand as tourism boomed but did nothing to protect waterways that were being overwhelmed by dairy effluent.
The National-led Government, he said, has moved from Labour's malign neglect to active destruction of the country's economic advantage.
He said Prime Minister John Key's idea of balance is to destroy the environment for GDP growth - which is an economic and environmental dead end.
'Failure to address inequality' deplored
On Saturday, Dr Norman's fellow co-leader, Metiria Turei, told the meeting that Mr Key is responsible for the failure to address inequality in New Zealand.
Mr Key has forgotten that he grew up in a state house, Ms Turei said, and has instead made cuts to the housing budget.
Similarly, she said, Social Development Minister, Paula Bennett, who was once a beneficiary, is denying women on their own with families the opportunities she had as a woman on her own.
Outlining the Greens' eight-point "Mind the Gap" proposal for reducing income inequality, Ms Turei said it includes a plan to build 6000 more state houses, make the first $10,000 of income tax-free and introduce a progressive power pricing system.