Britain's telecom and media regulator on Wednesday fined Royal Mail £21 million ($28.1 million), its largest penalty to date on the post and parcel group, for missing delivery targets for 2024–25.

The more than 500-year-old Royal Mail, whose iconic red post boxes with the Royal Crest dot Britain, has been trying to modernise operations to boost volumes, while the regulator, Ofcom, too, has revised some of its targets to prevent delays.

The group has missed delivery targets for at least seven years now. This is Ofcom's third consecutive annual penalty on the company, after it fined 5.6 million pounds for 2022-23 and 10.5 million pounds for 2023-24. The regulator did not levy any penalties on Royal Mail during the COVID-19 pandemic.

Ofcom on Wednesday also warned that the levies are likely to continue unless improvements are made by Royal Mail.

"Millions of important letters are arriving late, and people aren't getting what they pay for when they buy a stamp," Ian Strawhorne, director of enforcement at Ofcom, said in a statement, adding that the repeated failures were "unacceptable."

Royal Mail acknowledged the regulator's decision in a separate statement and said the pilot changes it has implemented to its "Universal Service" model have shown positive results.

Royal Mail is owned by International Distribution Services, which was taken private after its takeover by Czech billionaire Daniel Kretinsky.