Beaches in Salthill in Galway, Bundoran in Donegal, and Cork Harbour have been deemed litter black spots by the Irish Business Against Litter.
Speaking on RTÉ's News At One programme, IBAL spokesperson Conor Horgan said "fewer than half of Ireland’s beaches are clean".
An IBAL survey has found that while some popular beaches have improved, one in three are littered or heavily littered.
"Salthill and Loughrea beaches are littered. Bundoran, Bantry Harbour is Cork Harbour and Whitebay beach in Cork are heavily littered."
Mr Horgan said greater investment in bins, and supplementary bins for summertime can help to reduce littering, he said, adding that recycling facilities and designated picnic areas can lead to "a more orderly consumption of food, and a cleaner environment".
IBAL has said litter levels are contributing to "a pressing global issue of plastic pollution".
While 40% of 32 coastal areas surveyed were deemed 'Clean to European norms’, there was a rise in areas branded ‘littered’.
Beaches, harbours, rivers and their immediate environs were monitored by the Environmental Education Unit of An Taisce in June and July.
Among the clean beaches were Brittas Bay, Curracloe, Lahinch, Clogherhead, Portmarnock and Strandhill. By contrast, Bundoran, Keel in Mayo and Salthill and Dogs Bay in Galway were littered.
The seafront in Bray was praised in the survey, as was Kilmore Quay and Dún Laoghaire, however Kinsale, Bantry and Castletownbere harbours all failed to make the grade.
"The story is a positive one in that we've seen a welcome rise in the number of clean beaches and harbours compared to our study of 2 years ago," Mr Horgan said.
"This is especially encouraging given the number of people who are staycationing and availing of our coastal amenities this year. There is evidence that many local authorities have upped their game in terms of additional bins, facilities and signage."
"However, at the bottom end of the table, we’ve seen many areas deteriorate from 'moderately littered’ to ‘littered’.
The most common forms of litter found by the assessors were cigarette butts, sweet wrappers, disposable masks and plastic bottles, with coffee cups also featuring strongly.
IBAL said alcohol cans were found in almost half of all sites.
"The majority of these litter item are plastics, whose impact on the marine environment is a source of global concern," says Mr Horgan.
"Cigarette butts, for example, may appear harmless, but they are in effect a single-use plastic which poses a real danger to our sea life."