The number of racist incidents reported to the Immigrant Council of Ireland (ICI) increased by 11% last year.
The figure was revealed today at the launch of a new campaign encouraging people to report racism when they witness it.
The ICI said that just over a fifth of reported incidents took place on public transport, with most relating to passengers abusing transport staff.
The majority of such cases involved verbal harassment, including threats, but "elements of physical violence" were also frequently reported.
Some were punched, kicked, spat on or hit by objects.
In one case described by the ICI, a young woman of African descent was travelling by bus to college when a couple in their 20s began calling her racist names.
The man went on to rub a banana into the victim’s hair, ignoring an earlier intervention by the driver.
In another documented incident, a woman in her 40s verbally abused a bus driver who had called on her to pay her fare.
She used a number of racist slurs and threw a box with leftover takeaway food at him.
Taxi drivers of African origin also experience daily discrimination by passengers who pass them in the queue at taxi ranks, according to the ICI.
A third case highlighted by the organisation involved a black driver being continually overlooked by customers.
The man reported being passed over by potential passengers "four to five times" even after reaching the top of a taxi rank queue.
The 49 incidents on public transport made up just over a fifth of complaints received by the ICI last year.
Overall, 240 incidents were reported to the organisation in 2015, an 11% increase on 2014.
These ranged from verbal harassment (33%) to discrimination (23%) and physical violence (13%).
In 40% of the cases, the victim’s ethnic background was Muslim. A third of victims were of African descent.
The figures were highlighted at the launch of #StopRacism, a new joint initiative between the ICI and the National Transport Authority.
The campaign, which will be promoted through ads across transport networks nationwide, is being supported by gardaí, Dublin Bus, Iarnród Éireann, Bus Éireann and Luas operator Transdev.
"Racist incidents are under-reported, which makes it difficult to assess and tackle racism where it occurs,” said Brian Killoran of the ICI.
"The focus of our work with the National Transport Authority and our partners in public transport is to encourage people who witness racism to come forward, report it and receive support to address the issue."