BT, Plusnet, EE and TalkTalk were the most complained about broadband providers during the second quarter of 2016, Ofcom has revealed.
According to new figures from the regulator, the total volume of complaints it received against telecoms providers fell slightly between April and June.
However, broadband and fixed line services continued to generate the highest number of complaints during this time.
BT came top of the list with 26 complaints per 100,000 subscribers in Q2 - more than any other broadband provider.
Plusnet was not far behind, with 23 complaints per 100,000 subscribers, while EE and TalkTalk both racked up 21 complaints per 100,000 subscribers.
This meant they were well ahead of the industry average of 15 complaints per 100,000 subscribers.
Most of the complaints against these companies related to faults, service and provision issues, while many also arose due to concerns with charges, pricing and billing, as well as how they dealt with complaints.
Nevertheless, the figures were a slight improvement on Q1, when EE led the way with 34 complaints per 100,000 subscribers, while BT, TalkTalk and Plusnet generated 31, 30 and 27 complaints per 100,000 subscribers respectively.
Sky was the subject of the fewest complaints during Q2, with just five per 100,000 subscribers being received by Ofcom.
Virgin Media also performed strongly throughout the quarter, as it accounted for only seven complaints per 100,000 subscribers.
Lindsey Fussell, Director of the Consumer Group at Ofcom, said: "We expect providers to make customer service and complaints handling top priorities. While complaints have gone down, providers must work harder to better serve their customers.
"Consumers have a right to expect good service and will rightfully complain when that standard isn't met. If companies do fall short, we will step in and investigate, which can lead to significant fines."