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The cost of a first-class stamp will rise by 5p to £1.70 on 7 April, Royal Mail has announced.
It will also raise the price of a second-class stamp by 2p to 87p on the same day.
The company said the decision carefully considered "balancing affordability with the increasing cost of delivering mail".
Citizens Advice described the change as "yet another blow to consumers", and said the change to the second class price was "unjust".