The National Consumer Agency has found that six domestic waste collection firms had been operating "unfairly" as it secured undertakings that they will change contract terms for customers.

Some waste companies were exposing customers to unspecified charges and changing terms without a good reason, according to the agency’s consumer protection list for the first six months of 2013.

Branches of some of the State’s leading supermarkets were among recipients of a total of 40 enforcement actions issue by the agency for charging customers more than displayed and failing to display product prices.

The agency also convicted one Co Cork car dealer over the sale of a clocked car, according to the list it published today.

Six waste operators have undertaken to change their terms and conditions following the agency’s investigation into the contracts being offered to customers.

Among the terms which the agency “considered unfair” were “exposing consumers to unspecified charges, altering of terms and conditions without a valid reason, and terms not being drafted in plain English”, it said.

The waste operators involved were: The City Bin Company, Panda Waste, Greenstar , AES, Country Clean Recycling and Oxigen Environmental. The agency secured an undertaking from Greyhound waste late last year.

The agency found some 18 supermarkets and shops had charged more for goods than the price displayed and issued them with compliance notices. It issued five to Eurospar, four to Tesco, two to Dunnes Stores and two to Centra.

It issued fixed penalty notices to 22 supermarkets and shops for failing to display product prices, including six to Super Valu, five to Eurospar, two to Dunnes Stores, one to Tesco, one to Lidl and one to Fresh.

The agency also convicted car sales firm Damian Hayes Car Sales, Kanturk, Co Cork, for the sale of a clocked car. The customer was granted €1,750 in compensation for the false odomoter reading.

On publication of the list, National Consumer Agency chief executive Karen O’Leary said the organisation used its legislative powers “in the most appropriate and effective way possible - whether through securing undertakings; issuing compliance notices and fixed payment notices and, if necessary, taking prosecutions”.

The agency was committed to ensuring that consumer law and rights were “upheld to the greatest possible extent,”she said.