The UK’s major broadcasters are failing to meet best practice guidelines when providing subtitles for the live programming.

The first of four in-depth studies by Ofcom has showed that the BBC, ITV, Channel 4, Channel 5 and Sky need to make improvements if they are to meet the needs of people with hearing impairments.

Viewers have told Ofcom that poor latency in subtitling is particularly frustrating and the media regulator found that all of the broadcasters are some way off recommended guidelines.

The delay between speech and the corresponding subtitle was on average 5.6 seconds across all the broadcasters during live shows Ofcom monitored between October and November last year. This is well above the best practice guideline of 3 seconds.

C5’s news output was the worst offender, with subtitles being delayed by an average of 6.6 seconds. The BBC performed best with its live entertainment and chat shows, but the delay of 4.3 seconds was still above the recommended 3 second threshold.

However Ofcom found that the broadcasters are performing better in terms of words per minute and accuracy of subtitling. On the latter measure, the media regulator said that 98% of subtitling on live programming was correct.

Elsewhere, the broadcasters reported 400 technical failures between November 2013 and January 2014, each of which led to temporary loss of subtitling. This, Ofcom said, backed up viewer complaints that outages are not always a problem with their television set.

Ofcom also raised concerns about the quality of subtitling on pre-recorded shows, particularly those produced at short notice for broadcasters.

“Ofcom remains concerned that subtitling may not be treated in all cases as an integral part of the production process, even though it is just as important to hearing impaired viewers as, say, matching voiceovers to pictures is to others. The result for viewers who rely upon subtitling is that the quality of their viewing experience is inferior to programmes with pre-prepared subtitles,” its report said.