Passengers have registered 610 complaints about taxis since the start of this year.
They include accusations about sticky seats, unpleasant smells and filthy vehicles.
New figures provided to the Irish Examiner by the National Transport Authority (NTA) show 229 complaints were about taxi driver behaviour.
A further 214 complaints were made about overcharging and other fare matters.
One complaint concerned a driver who did not provide the option of accepting a fare by credit card.
The passenger said the driver made them go alone to an ATM, shouted at them and charged €2 more for wasting time.
In response, the NTA issued the taxi driver with a fine for failing to offer a receipt.
The total number of complaints between January and June this year was 610, which compares to 629 complaints for the same period last year.
In total, the NTA has imposed 820 fines - totalling €25,900 - on drivers who broke the rules during the first six months of this year.