Navan, Co Meath, has emerged as a "litter blackspot" for the third time in a row, according to the latest Irish Business Against Litter (Ibal) survey.
The only other town in the Republic to be classed as a litter blackspot is Newbridge, Co Kildare.
The survey of 50 towns and cities across the State, carried out by An Taisce, found Carlow to be the cleanest town, with 18 areas deemed litter free.
Dublin has been omitted from the 2007 litter league, but will be compared against other cities in a European league to be published later this year.
Ibal has identified dumping from private cars as a major cause of concern and has called for drivers to be given penalty points for dumping offences.
It said places such as Killarney, Athlone, Cork, Limerick and Nenagh suffered badly from litter on approach roads, which brought down their overall rankings. "In many cases, the town councils and city councils are doing their bit in keeping the streets free of litter," said Ibal chairman Tom Cavanagh.
"However, they are being frustrated in their efforts for a clean environment by litter on approach roads."
He continued: "The impression of a town is coloured hugely by what one encounters on approaching it. For this reason, we need to find ways of targeting those who dump or litter from their vehicles."
In addition to suggesting penalty points for litter offences, Mr Cavanagh proposed building lay-bys equipped with bins on motorways, "to facilitate truck drivers who often have their meals on the go".
Overall, Ibal found that litter levels had improved by 2 per cent compared with the same period last year. The average cleanliness rating is now 75 points, within sight of the 80-point mark, which is deemed "clean to European norms".
The organisation warned that the summer season was a critical time for litter, with Fáilte Ireland reporting that the majority of tourists find Ireland to be less clean than they expected.
Fáilte Ireland's Tourism Matters publication suggests that more than a quarter of tourists to Ireland had experienced litter or dumping in the countryside. German holidaymakers are least likely to agree that Irish streets are cleaner than streets in their home country. "This is simply not a basis to build future tourism on," Mr Cavanagh said.
