Royal Mail has announced it will hike the price of first-class stamps by 30p due to "very real and urgent" financial challenges.
The increase, which will kick in from 7 October, will see the price of a first-class stamp rise to £1.65p, while second-class stamps will remain at 85p.
The company said it was facing pressure from declining letter volumes and rising business costs in maintaining the one-price-goes-anywhere universal service.
It has called for the service terms, under which it is legally obliged to deliver letters six days per week, Monday to Saturday, and parcels Monday to Friday, to be reformed.
"We always consider price increases very carefully. However, when letter volumes have declined by two-thirds since their peak, the cost of delivering each letter inevitably increases," said Nick Landon, chief commercial officer at Royal Mail.