Comcast blamed telecom competitors for unexpectedly slower growth in subscriber additions in the third quarter.

The cable giant added 662,000 new voice-over-IP customers in the quarter, up from less than half a million a year earlier but down more than 1% sequentially. In what is typically a strong season, net broadband subscriber additions were up 5% sequentially to 450,000 but down 16% from a year earlier.

Brian Roberts, Comcast’s chief executive officer, blamed the deceleration on “increasing competition and a softer economy.”

Comcast also lost 65,000 basic cable subscribers during the quarter, after gaining 11,000 in the same period a year earlier.

More than 60% of Comcast’s net broadband subscriber additions came from DSL substitution, the company’s highest rate ever.