Royal Mail has been accused of discriminating against modern families after it was revealed to be charging couples with different surnames double for redirecting their post.

Citizen’s Advice slammed the service for penalising unmarried couples, same-sex partners and blended families by charging per surname, rather than per household for its mail distribution service.

The pricing structure means that while a ‘nuclear family’ would only pay £33.99 for a three-month subscription to the service – aimed at those who have recently moved house – non-traditional families could be charged multiple times.

Data from the Office of National Statistics suggests around one in three (32 percent) of families in the UK fall outside the ‘traditional’ structure.

But the addition of just one extra surname makes the service more expensive than any other country, the watchdog found. The Netherlands is the only other country in Europe to charge per surname.

“Many people rely on Royal Mail’s redirection service, yet it’s designed for households of the past,” said Gillian Guy, chief executive of Citizen’s Advice.

“Consumers are facing a double whammy.  Royal Mail has drastically increased the price of redirection over the years, but hasn’t changed its outdated price structure that assumes families always share the same surname.”

Research for the watchdog found that 55 percent of people who moved house within the past two years live with at least one person with a different surname.

Royal Mail has now agreed to change its pricing structure. A spokesperson for the postal service said: ”We agree with Citizen’s Advice that there is a need for a different pricing structure.

“We wrote to Citizens Advice last week, before the report was issued, to confirm that we will change the pricing structure of our popular Redirections service away from a per surname basis or anything similar.”

They added: “We are currently working on the details of this new pricing structure and will share once finalised.”