Ofcom said the Post Office breached a rule that gives people with impairments the right to access comparable phone call services as those without impairments.

The regulator said that between August 2013 and November 2018, the Post Office broke this rule by failing to put in place a special price scheme for calls made by customers with impairments who needed to use relay services, meaning they were overcharged unfairly.

Relay services help people with hearing and speech difficulties to communicate over the phone, by offering text-to-speech and speech-to-text translation services. A special price scheme compensates them for the additional time it takes for them to make phone calls using a relay service.

As well as the fine, Ofcom is also requiring the Post Office to refund customers who were affected.

Meredith Sharples, director of telecoms at the Post Office, said: “The Post Office apologises to any of our customers who made text relay calls using our service and did not receive the discount that they were entitled to. Up to 126 customers a year were affected and where possible we have refunded customers the full cost of any calls made. We now no longer apply any charge to calls made using this service.

“The Post Office has always provided text relay services and we recognise the important role they play for anyone who may have hearing or speech impediments. We reported this over charging matter to Ofcom in January 2019 and have co-operated fully with their investigation.”