Fearing their severely depleted service could suffer even more if it becomes less affordable for the public, taxi unions are set to meet tomorrow to discuss how to respond to the proposed changes.
The NTA is inviting submissions on the matter from any interested parties, including the public, but the deadline is next Monday at 5pm.
Taxi fares are reviewed every two years, and were not changed in 2010.
Under the current flat rate system, when a person gets into a taxi the fare starts at €4.10 which covers the first kilometre. Then the passenger is charged €1.03 for each additional kilometre, up to a distance of 15km.
The NTA is now proposing that the flat-rate charge be reduced to €3.60 for the first half kilometre, but thereafter the fare would be €1.10 per kilometre. There are also proposals to vary fares in a similar way for journeys over 15km.
"A lot of taxi drivers are not happy with the new proposals," John Usher, president of the Irish Taxi Drivers' Federation told the Herald.
"The fear is that nobody has any money, and we ask that the NTA not increase fares which would make it even harder for people. From what I can see, the drivers I have consulted say they are afraid of what the move could do to the business."
While the NTA's research has found that costs for taxi drivers have increased by nearly 4pc, mainly due to fuel costs, it has also found that three-quarters of taxi drivers and taxi companies do not want fares to go up.
Its statistics also show that more than a quarter of the public interviewed say their taxi usage has dropped, saying cabs are too expensive, people have less money to spend, and they don't go out as much.
On top of that, the numbers who would say taxis are good value has halved since 2008 from 62pc to 32pc.
When the NTA asked members of the public in a survey what would make them more likely to use taxis, more than 40pc said cheaper fares.
A meeting of the five different taxi drivers' representative bodies is to take place tomorrow morning to discuss the NTA's proposals.
A spokesperson for the NTA said the proposed changes were only at consultation at this point, and that anybody can make submissions on the NTA website, or by writing to them in Harcourt Lane, Dublin 2.