Comcast, the nation’s largest cable operator, announced today that it has passed Qwest as the nation’s third-largest residential phone provider.

Comcast’s digital voice offering now serves 6.47 million customers, which exceeds Qwest’s reported residential subscriber base. Comcast said it has added residential subscribers in each of the last 12 quarters.

“Consumers are switching to Comcast’s Digital Voice Service because of our low prices, reliable service and innovative features,” said Cathy Avgiris, senior vice president and general manager of voice services for Comcast.

“Comcast Digital Voice is reinventing home phone service for the 21st century, and we are thrilled that millions of consumers today are choosing Comcast for home phone service,” Avgiris continued. “We now offer features that integrate with our video and high-speed Internet products, and we’re deploying a next-generation cordless phone that lets customers do more than just make phone calls.”

While cable operators have eaten into the landlines of large telcos such as AT&T and Verizon, Comcast said consumers have benefited from the increased competition. A study by economic consulting firm MiCRA found that consumers saved $13 billion alone in 2007 because of phone competition from companies such as Comcast.