The attack left a deep gouge on the side of the kauri, with a cut spanning the tree's circumference.
A Save Our Kauri spokeswoman, Aprilanne Bonar, said it had put Mr Smith's life at risk.
On Monday, Save Our Kauri applied to the High Court for a judicial review and was negotiating with the developers until late Tuesday night.
Ms Bonar said the group believed the talks had resulted in an agreement not to fell the tree.
"We were of the understanding that all parties had agreed on a course of action in going forward."
She said police were investigating the incident. Police involved could not be reached for comment.
Later yesterday afternoon, an interim injunction was granted halting all activity onsite until a hearing.
The substantive case will be heard on the next available date after February 26 next year.
The controversy began in March when the owners of the property, John Lenihan and Jane Greensmith, planned to chop down the 200-year-old kauri and a 300-year-old rimu.
They came to an agreement with the council and protesters after Michael Tavares spent three days in the kauri.
Mr Smith will appear in the Waitakere District Court on January 6.
He returned to the site yesterday after he was granted bail to assist with "regrafting" the kauri in the hope of saving it.
Mr Smith, an aborist, said the wound on the tree was significant and he was unsure if it would survive.
The wound on the tree was significant and Mr Smith was unsure if it would survive.
In light of the day's events, members of the Titirangi community gathered last night for a vigil for the tree.
Ms Bonar said the community were also coming together to "reflect" on what had happened.
"We need each other's mana/heart to ensure our [kauri] is protected."
Mr Lenihan and Ms Greensmith could not be reached for comment.
Unkindest cut
• A kauri tree at the centre of a legal dispute was "viciously attacked" yesterday morning, by a group who ringbarked it.
• Tree protester Johno Smith was in the canopy of the tree when the incident occurred. Footage taken by him shows members of the group beginning to ringbark the tree. Mr Smith can be heard pleading with them to stop.
• Following the incident Mr Smith handed himself into police and was charged with trespass and bailed. He will appear in the Waitakere District Court on January 6.
• The High Court yesterday afternoon granted an interim injunction against the felling of the tree, the Save Our Kauri Community Group said. Spokeswoman Aprilanne Bonar said that meant all activity on site has been halted until a hearing.