Passenger complaints included a "frankly disgusting" smell inside a car and concerns over an "extremely filthy" taxi
Almost a thousand people made an official complaint about a taxi last year.
Customer criticism ranged from reports of bad hygiene to overcharging and aggressive behaviour.
New stats from the National Transport Authority show some drivers have even been accused of refusing to take guide dogs.
The data - released to the Irish Independent following a freedom of information request - show a total of 998 complaints last year.
Taxi drivers paid a total €56,005 in fines or 'Fixed Charge Penalty Notices' - ranging from €40 to €250 - in 2016, up 38% on 2015.
There were 444 complaints about driver behaviour, alongside 348 complaints relating to 'fares matters'.
34 complaints, meanwhile, were related to the condition of taxis - one complaint referred to the "frankly disgusting" smell inside a car, while another passenger complained of an "extremely filthy" taxi.
President of the Irish Taxi Drivers Federation, Joe Herron, spoke to Newstalk Breakfast about the number of complaints - but he suggested he is not surprised.
"The number of complaints about driver behaviour is actually down, as are the number of complaints about vehicle condition," he said.
He encouraged people to download the Driver Check app.
Joe explained: "With the website, it has become a lot easier to make complaints about drivers - and people tend to do [that].
"I also looked at the number of drivers that were prosecuted for driver behaviour - and there was in fact only one prosecuted for it. I would say the vast majority of these complaints, there is no follow through on them - they are fully investigated, but it's found there is nothing wrong with them."
He added that he believes drivers smoking in their vehicles is "totally unacceptable", adding there is quite serious consequences for it - citing a fine of up to €3,000.
He also explained that they hear some terrible stories from drivers about passengers.
"Most taxi drivers expect they're going to get some sort of verbal... I won't necessarily say abuse, but things they wouldn't like to hear from passengers."