BT has apologised for the service problems experienced by some viewers during the BT Sport launch in summer 2013.
Latest data from Ofcom reveals that BT saw a significant increase in the number of customer complaints during Q3 2013 - up from 0.26 per 1,000 TV customers to 0.56 during the third quarter.
Almost half of the issues raised related to BT Sport, which launched on August 1st this year. Other complaints about BT TV largely concerned service issues and complaints handling.
A spokesperson for BT said the main reason for service issues was "the unprecedented volume of interest in BT Sport".
She added that the firm's efforts to provide availability on multiple TV platforms in "a very short space of time" had also caused some difficulties.
"Also, some customers were confused by us initially making BT Sport available free to air on BT TV and then encrypting the channel," the spokesperson stated.
She said the complaints represented "a fraction of one per cent of those customers", adding that BT is now seeing much-reduced levels.
Sky was found to be the best performer in the pay-TV market on customer service during Q3 2013.
The service provider received just 0.02 complaints per 1,000 registered viewers, while Virgin Media was also below the industry average at 0.05.