439 complaints were made to the taxi regulator since November - most of them relating to passengers being overcharged.
Bad smells, sticky door handles and stained back seats also featured among the complaints - which were contained in a report from the National Transport Authority.
Taxi drivers say it's unacceptable, but add some passengers have picked their nose, vomited or dragged mud into cars.
Jim Waldron from the Private Hire and Taxi Association says there are procedures in place to investigate complaints:
"You can be fined €80 by the NTA. What they'll do is call you in for an inspection on your car.
"If you still had that bad condition of a car you would be fined for it.
"They are generally followed up with people bringing complaints."