An 11-year-old child was ditched off a Naked Bus without her bags in the dark.

The grandfather of an 11-year-old girl kicked off a bus in the dark in unfamiliar Auckland streets says long-haul company Naked Bus needs to sort itself out.

Tiffany Cave, 11, was travelling from Rotorua to Auckland on Monday to stay with her grandparents for the school holidays.

She was supposed to meet her grandmother at Manukau but the 11-year-old had fallen asleep and missed her stop.

Despite being aware the unaccompanied minor was on his bus - the family had signed all Naked Bus documentation need for an unaccompanied child - the driver failed to check on her at Manukau.

Then, when Tiffany woke up a couple of hundred metres after the missed stop and alerted the driver, he pulled over and dropped her on the side of the road in the dark, without her luggage, about 8.45pm.

"Who in their right mind does that?" Tiffany's grandfather Doug Healey said.

"She [Tiffany] was distraught. She's come from Rotorua, it's a little place. And she's in Auckland.

"When the bus left ... she's lost. She could've turned [and walked] in any direction and then everyone has lost her.

"We're lucky that we got her, that we found her."

A Naked Bus spokeswoman said the driver had been stood down and the company was investigating.

"The investigation is in full swing," she said on Friday morning.

"We deem passenger safety the most important thing to us. They take the report [of this incident] very seriously."

Grandmother Lian Healey had been waiting at the Manukau bus stop but Tiffany never got off. Naked Bus knew Tiffany was an unaccompanied child and had assured she would be taken care of, Doug Healey said.

"She [Lian Healey] was panicking frantically. She couldn't get hold of anyone from Naked Bus for at least 20 minutes, and when they did answer they couldn't give her any information about the route, they couldn't get hold of the driver, no one could help."

Not knowing what to do and about to drive into central Auckland to meet the bus as a last resort, the grandmother heard Tiffany - wandering alone and without her luggage - calling out to her.

Her grandfather said Tiffany had been woken by a male passenger beside her who asked if she was supposed to have gotten off at Manukau.

She went down the bus stairs from the top deck with the man to alert the driver.

"The driver opened the door and told her to get off the bus. She says, 'Where's my bag?' He said, 'I probably left it in Manukau.' He left her on the street and drove off," Healey said.

Tiffany and her grandmother had to then drive into Auckland city to get the suitcase off the bus - which the driver had not taken off at Manukau.

Healey said the bus company needed to improve its processes.

"They need to reassess. They need to review their policies ... the whole shebang. The company is responsible for this."