Tom Espiner
Business reporter
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Royal Mail can deliver second-class letters on every other weekday and not on Saturdays to help cut costs, the industry regulator has said.
Ofcom said a reform to the Universal Service Obligation (USO) was needed as people are sending fewer letters each year, so stamp prices keep rising as the cost of delivering letters goes up.
The current one-price-goes-anywhere USO means Royal Mail has to deliver post six days a week, from Monday to Saturday, and parcels on five from Monday to Friday.
Royal Mail welcomed the changes, saying it would support a "reliable, efficient and financially sustainable Universal Service".
Ofcom said Royal Mail will have to continue to deliver first-class letters six days a week.
"These changes are in the best interests of consumers and businesses, as urgent reform of the postal service is necessary to give it the best chance of survival," said Natalie Black, Ofcom's group director for networks and communications.
However, just changing Royal Mail's obligations will not improve the service, she said.
"The company now has to play its part and implement this effectively."
The regulator is also making changes to Royal Mail's delivery targets.
The company will have to deliver 90% of first-class mail next-day, down from the current target of 93%, while 95% of second-class mail must be delivered within three days, a cut from the current 98.5%.
However, there will be a new target of 99% of mail being delivered no more than two days late to incentivise Royal Mail to cut down on long delays.
Royal Mail owner International Distribution Services (IDS) welcomed the Ofcom announcement, saying it was "good news for customers across the UK".
Martin Seidenberg, IDS chief executive, said the changes follow "extensive consultation with thousands of people and businesses" to reflect their needs and the "realities of how customers send and receive mail today".