The Royal Mail has called for timely "regulatory action" to prevent the impact of direct delivery competition from undermining the economics of the Universal Service, after a challenge to the watchdog from delivery rival TNT.
Ofcom is investigating a complaint from TNT over Royal Mail's decision to change conditions and increase the prices it charges to deliver post collected and pre-sorted by its competitors.
Royal Mail chief executive Moya Greene said:"Royal Mail is required to deliver six days a week, overnight, throughout the whole country, to stringent quality standards and at a uniform, affordable tariff.
"Moreover, we are also required to deliver any items TNT Post UK does not consider economic to deliver itself. If TNT Post UK is successful in delivering its stated objectives, this could threaten the fundamental economics of the Universal Service."
More top news
Southern areas windy and very mild.
Nobel-prize-winning schoolgirl Malala Yousafzai has said she is a proud Brummie, as a new portrait of her was unveiled in her adopted home.
The Filipino girl group lost out to Lauren Murray in the sing off after receiving the lowest number of votes.