The price of a first class stamp is set to rise by 10 pence, which means people will have to spend 95 pence to send a letter. Second class stamps will also increase, this time by two pence to a 68 pence total.
Royal Mail explained the move was as a consequence of delivering to more addresses, which was adding to costs.
The changes are set to come into force from April 4 onwards.
April will mark a month of rising prices for Britons as the cost of living begins to bite.
Energy prices are set to rise, alongside National Insurance rates, and inflation is predicted to hit nearly eight percent.
READ MORE: WASPI women fear free prescription age increase
Twitter user @Sour_and_Grump said: “Way to go Royal Mail – address falling letter volumes by imposing inflation busting rise in price of stamps.”
@JeremyGasson referenced the rising cost of living, expressing his shock at the increase.
He stated: “That’s almost a 12 percent rise – very helpful for everyone in current climate – how can this be allowed and justified?”
@JuliaWindsor3 wrote: “There are people out there who have no choice but to use the Royal Mail and are being royally punished for it, they simply won’t be able to afford it.”
While @buffybatik remarked: “Goodness! I’m old enough to remember them being 3p!”
Nick Landon, chief commercial officer at Royal Mail, stated the organisation needed to balance pricing against declining letter volumes and the cost of delivering to more addresses.
He added: “As customer needs change and we see a greater shift from letters to parcels, it is vital that the universal service adapts to stay relevant and sustainable
“These price changes are necessary to ensure we can continue to maintain and invest in the one-price-goes-anywhere universal service for future generations.”