Royal Mail is to raise the price of stamps, months after the government completed the privatisation of the service.

First class stamps will go up by 1p to 64p, while a second class stamp will rise by the same amount to 55p from 29 March.

The company said it had “carefully considered” the impact of price rises on customers and its own business, opting to apply the “smallest possible increase”. The price of large letter stamps will also rise by 1p.

“We believe these changes are necessary to help ensure the sustainability of the universal postal service,” the company said, adding that stamp prices in the UK are among the best value in Europe.

The price of a first class stamp in the UK remains well below the European average of 78p, and less than the 64p average for second class letters, Royal Mail said.

Stamps have more than doubled in price over the past 20 years, with increases applied during Royal Mail’s time as a state-owned company and since its privatisation.

A first class stamp cost 26p in 1995, adjusted for retail price index inflation.

The government sold off its remaining 13% stake in Royal Mail for £591m in October, completing a controversial privatisation process that began in 2014.

The postal service’s stock market float drew criticism over claims that the former business secretary Vince Cable sold it off too cheaply.