Taxi drivers were accused of six violent sexual attacks on the public in the past year, a figure described by an industry leader as disturbing.
The sexual assault allegations are among 184 complaints made to the Transport Agency in the year to June 30, a quarter more than received by the agency in the previous year.
The total number of complaints not only increased by 37 when compared with the year to April last year, but allegations were also more serious.
In the year to April 2012, the most serious complaints included a sexual harassment and 11 of unacceptable and intimidating behaviour.
But in the past year complaints made to the agency included nine of assault, four sexual harassment, three of drunk or drugged drivers and two of dangerous driving.
Complaints were also made about aggressive driving, overcharging, refusing fares and using a cellphone while driving.
Taxi Federation executive director Tim Reddish said bad behaviour from drivers had to be "dealt with".
The sexual attacks were most disturbing, Reddish said.
"I thought we were past that with the cameras in there now.
"I'm staggered and extremely disappointed that anyone thinks they can get away with it."
He believed the installation of cameras was partly responsible for the increase in complaints.
However, the Herald on Sunday revealed in June that hundreds of faulty security cameras had been installed in taxis.
A 23-year-old woman told the New Zealand Herald last month that she was indecently assaulted by a taxi driver in March, but the allegation could not be proved because footage taken inside the cab was missing.
Reddish said the number of complaints was small considering the "millions" of journeys made each year.
"Auckland Co-op Taxis alone has 700 cabs, with each driver probably making 20 to 25 journeys a day, six days a week."
Agency spokesman Andy Knackstedt said it was disappointing more complaints were being made.
Allegations of criminal behaviour were passed to police, but the agency was also concerned about complaints over the level of service provided.
"Everyone should have confidence that they can hire a taxi so they can get to their destination safely."
Anyone with concerns about a taxi driver or company should contact the agency, he said.
Figures for complaints in previous years are not easily available as there is no national database and some older complaints are held off-site from the agency's regional offices.
Miki Thompson drove taxis on and off for 43 years before retiring last year aged 87.
The Invercargill man still holds strong views about the industry.
"I think it's gone to the dogs. When the industry was deregulated 18 to 20 years ago, that's when we started getting complaints.[The Transport Agency] seem to be licensing everybody now."
Before deregulation most taxis were operated by owner-operators, who had to stay professional to protect their livelihood, Thompson said.
Later opening hours for pubs and bars also played a part.
"There's fault on both sides sometimes."