Royal Mail has warned daily deliveries are under threat because of cut-throat competition.
The postal giant, which has seen its profits slump by £74million, says allowing rivals to cherry pick lucrative business contracts could make its six-day-a-week service no longer viable.
Royal Mail, unlike its competitors, must deliver to everyone in the country for the same price.
The company is calling on industry regulator Ofcom to urgently review the rules.
Royal Mail claimed rapid expansion by arch rival Whistl, formerly TNT, could reduce its revenue by £200million by 2017.
Royal Mail slump
Whistl has begun doorstep deliveries in large cities but not every day or in rural areas.
Royal Mail boss Moya Greene said this “undermines the economics” of its nationwide delivery service.
Potential changes could see Royal Mail only delivering five times a week or being paid a subsidy.
Today’s warning makes a mockery of claims by Business Secretary Vince Cable that privatising Royal Mail would safeguard universal delivery.
Royal Mail also highlighted the threat from Amazon, which has begun delivering its own parcels.
Royal Mail said profits had dropped by 21% to £218million in the six months to the end of September.
Chuka Umunna, Labour’s Shadow Business Secretary, said: “The Tory-led Government’s fire sale of Royal Mail has put the essential services which consumers and small businesses rely on at risk.
“David Cameron’s promises to protect services are looking less and less credible by the day.
“This warning is deeply concerning and comes after consumers have already been hit with changes in collection times, with many last collections moving earlier in the day.”