"While even one complaint is too many, it is important to acknowledge that this report is a raw measure and as the Commission acknowledges, not all complaints indicate there is an issue," a spokeswoman said.
Spark also expressed disappointment to be ranked highly, but said it has made significant improvements in customer service over the period the Com Com report covers.
"We are focused on resolving customer complaints without them having to recourse to other bodies such as the Commission. I'm pleased to say that the vast majority of customers have their complaints resolved simply by talking directly to Spark," a spokeswoman said.
Telecommunications Forum chief executive Geoff Thorn said a number of issues stem from the large and complicated nature of the industry which is "changing all the time."
Thorn acknowledged some issues in the customer service space, but said the TCF had been working with telcos to improve consumer interactions.
Customers also complained about termination fees on fixed-term contracts.
The public made 403 complaints about appliance retailers including 82 about Noel Leeming, 45 complaints about Harvey Norman and 32 about PB Technologies.
"Some consumers... complain about a lack of availability of well-priced sale items, making some suspect that certain sale offers on highly desirable products are bait advertising to bring customers into the store," the commission said.
More than 350 complaints were made about motor vehicle dealers and 155 about electricity retailers. A similar amount of gripes received about supermarkets, which generated 150 complaints.
Given consumers are buying more products online, the commission unsurprisingly received more complaints about purchases from websites.
"Consumers complain about difficulty in determining (often after a purchase has been made) whether the trader had represented price, goods or services accurately, especially as online pricing can appear substantially cheaper when compared to traditional bricks and mortar retail stores," the commission said.
It is evident from some complaints that consumers have subsequently had doubts about whether they purchased from a legitimate trader, particularly if the trader is based abroad and the consumer has been unable to make contact with the trader to resolve concerns about product delivery or quality," the regulator said.
"We also note an increase in complaints about traders failing to deliver products at all, or consumers being 'scammed' by online traders. There is a degree of trust required on the part of the consumer when making purchases online. Consumers' 'trust in trade' online may decrease if more consumers are 'burned' by negative experiences," the report said.
Travel and tourism booking agents - most of them online-only - were the subject of increasing number of complaints across the year with people upset about the quality or nature of things like accommodation which they booked.
The number of complaints about warranties and guarantees for goods or services was up 160 per cent in the last year.
When it came to complaints about sales methods, online retailers made up nearly half of those received by the commission. Instore sales made up 25 per cent while telephone sales accounted for 13 per cent of complaints.
