Auckland Transport spokesman James Ireland said the treatment of passengers demonstrated in the incident was "unacceptable" and said AT was investigating.
"Auckland Transport has spoken to the bus operator who are investigating this and will be meeting with the driver this afternoon."
After berating the group for their behaviour, the driver had then insisted they exit the bus on Great North Rd, leaving them stranded well short of their Henderson destination.
Holliday said the driver had initially pulled up outside Sky City and waved his arms at the group seated at the back of the bus and again near the Auckland City Mission.
When the group asked what was wrong the bus driver stormed to the back of the bus and said: "You are all acting like animals and this sounds like a fish market. You must stop talking so I can concentrate."
Holliday said the walkers were silent for a time but decided it was too absurd and began their conversation about their outing.
Not long after the driver pulled over and switched off the ignition and refused to restart until the pensioner group tagged off the bus.
When asked what the problem was the driver accused the group of being drunk and unruly and said "he couldn't understand us because we came from a different country".
Holliday flatly denied the accusations of drunkenness.
"He said we'd been drinking and we were acting like idiots.
"The strongest thing we had to drink all day was two cups of coffee."
She said the bus was held up for 10 minutes during the stand-off. The group decided to get off the bus apologising to fellow passengers. Three others got off in sympathy.
Holliday said the group managed to get home on the next bus to Henderson. She said the episode had upset the walking group.
"Everyone is traumatised by the incident. We couldn't sleep," she said.
The group immediately filed complaints against the driver with Auckland Transport.
A spokeswoman from the bus company, Pavlovich Coachlines, said she couldn't comment on what was an "internal disciplinary process".
"I understand the customers are in communication with Auckland Transport."