A survey of over 50,000 home broadband and telephony users by utility comparison service uSwitch suggests that satisfaction levels have fallen by an average of nine per cent for broadband and four percent for telephony services since March.
The satisfaction gap between the top and bottom players is 15 percent for broadband and 11 percent for telephony.
Orange and Carphone Warehouse, both of which have launched 'free' broadband products this year, came bottom of the survey with 70 percent overall customer satisfaction.
Carphone Warehouse's TalkTalk also came bottom of the survey for customer service with 42 percent, and Orange was next worst with 46 percent.
Virgin.net was the best performing supplier overall, according to the survey, with 85 percent in overall customer satisfaction.
"Virgin only started bundling a month ago and it seems that, because it has concentrated on broadband and not been distracted by other services, its customer service level has remained high," Steve Weller, head of communications services at uSwitch, told vnunet.com.
Despite offering 'free' broadband, Orange also came bottom in the survey for value for money. The results throw into doubt the value of 'free' services to customers and suppliers.
The biggest suppliers, BT and NTL, which account for 14.7 million customers between them, also saw customer satisfaction levels fall.
BT fell from 82 percent in March to 76 percent in November, while NTL fell from 81 percent to 72 percent over the same period.
The past 12 months have been characterised by suppliers going all out to recruit customers with price cutting and bundling.
Some £134m ($335m) was spent on advertising broadband services in 2006, compared to £105m ($262) in 2005. But suppliers will have to compete on service next year, the report predicts.
"Suppliers will have to take notice of these figures and provide a better customer service experience," said Weller.
"We have seen broadband suppliers differentiate themselves on price until now, but we think that equipment, service and support will matter more."
USwitch reported that there were 10 million UK broadband users in March, and that the figure will rise to 11.7 million by the end of 2006.
This growth means a greater number of customers without technical know-how, further emphasising the need for better customer service.
"Customers are not looking for the cheapest service, they are looking for value," said Weller. "The audience is becoming less technically savvy and will require more help and hand-holding."
The trend for bundling services will also reduce customer churn, according to uSwitch, as the deals will tie customers to suppliers.
"Ofcom will need to look at how customers make a seamless transfer from one bundle of services to another," said Weller.