Dublin Bus services through College Green are being delayed by up to seven minutes at peak times as buses, Luas Cross City trams, cyclists, cars and pedestrians all compete for road space.
Congestion in the city centre arising from the introduction of new tram services between St Stephen's Green and Broombridge has delayed bus services.
In some cases route changes have resulted in no improvement, Dublin Bus has confirmed.
Although 17 services have been diverted away from Coll-ege Green in recent weeks in response to concerns about congestion, Dublin Bus said it had led to only limited improvement.
"Since early December, during the morning peak, our services through College Green were taking an additional one to three minutes," a spokesperson said.
"This increased by a further three to seven minutes in mid-January.
"After the route changes were implemented on January 29, some routes improved by up to four minutes in the area, while others have not improved."
The National Transport Authority (NTA) said it will consider banning taxis and diverting more bus routes after complaints since Luas Cross City opened in December.
A spokesman said the NTA would "look at everything" to ensure public transport services operated freely, which could include banning taxis from College Green.
Signalling systems are also being reviewed in the city centre following problems with a new 55-metre-long tram, one of which became stuck on O'Connell Bridge last week.
The NTA said it has been in continuing discussions with Dublin Bus and the city council about traffic arrangements since Christmas, but there are fears that gridlock will worsen when more of the longer trams enter service later this year.
"We would acknowledge there are issues and there is congestion, but it's a very complex set of junctions. We're looking at ways of mitigating congestion there," a spokesman said, adding that diversions to 17 bus routes introduced in recent weeks have had an impact.
Asked if taxis could be banned, the spokesman said it was within the powers of Dublin City Council to do so, adding: "We will look at everything."
Some transport sources have suggested delays in developing the College Green Plaza, which would remove cars from the area, had exacerbated delays during peak times.
Others have noted that Luas Cross City was planned before the plaza was announced.
Dublin Bus said it was working with the NTA and Dublin City Council on solutions to alleviate the delays.