Ofcom has ruled that Channel 4 broke its licensing conditions after viewers were forced to go without subtitles, signing and audio description.
The TV watchdog said that the broadcaster had missed its subtitles quota last year when a fire at a broadcast centre disrupted their services.
The broadcaster experienced a number of major problems from September to November, caused by issues at the centre which handles its playout services.
In a statement, Channel 4 said they were 'very disappointed' with Ofcom's findings and will 'review' the ruling.
The broadcaster also said sorry to their viewers: "We would like to apologise once again to our audiences for the disruption."
Channel 4's statement also said since "the catastrophic incident last September... we have implemented a number of new systems and processes to avoid a serious incident in the future."
Ofcom also found that the broadcaster breached another term of its licence by not communicating with the audience affected by the outage.
Channel 4 did not share information with its viewers for 12 days.
The regulator called Channel 4's communication 'severely lacking'.
There is a statutory requirement for 90% of Channel 4's output to feature subtitles which it fell short of due to outages between September and November. Only85% of Channel 4's broadcasting hours featured subtitles.
In a statement, Ofcom said: “An Ofcom investigation has found Channel 4 breached the conditions of its broadcast licence following an extended outage of its subtitling, signing and audio description services. These ‘access services’ are relied on by millions of people to watch and listen to television, including those who are deaf, have hearing loss, are blind or partially sighted. Our investigation found that, as a result of an incident at a broadcast centre run by Red Bee Media, Freesat audiences who rely on subtitles were unable to fully access Channel 4 programmes for nearly two months.”
The incident at the broadcast centre also affected broadcasts by the BBC and Channel 5 but their services were restored much quicker.
Channel 4's back-up system also failed to work properly and viewers had to wait up to 8 weeks before subtitles returned to the broadcaster.
The channel must now report to Ofcom by the end of the year on the steps it has taken to ensure its subtitling services are more resilient.
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