A British Bank has become the first in the world to offer a third gender option for 'non-binary' customers

Britain's Metro Bank has become the first in the world to allow customers to sign up to its services under a third gender.

There will now be three options available on application forms: male, female, and non-binary.

Non-binary is the term used for individuals who don't identify as either male of female.

The bank has also added the title "Mx" alongside Mr, Mrs, Miss, and Ms.

The Mx title is often used by transgender or non-binary people, who also often prefer to be called by gender-neutral pronouns such as they, their, and them.

The decision, which we first heard about on Buzzfeed UK, was made after a Scottish teenager was not able to open an account because her only option was to tick either the male or female box.

Earlier this year, Kaelin Fanish explained to Buzzfeed: "[When you] only see those two boxes then you don't see yourself there. You are absent. That must hurt, and that's what makes me angry."

The teenager hailed the historic move as a "massive step forward" for a 600-year-old banking system which has always provided only two options to customers.

Jack Monroe, a campaigner for non-binary recognition, also called the introduction of trans-friendly options a "positive step" that is "carving a new path for traditional banking models."

Metro Bank's chief people officer, Danny Harmer, told Buzzfeed UK: "One of the things at Metro is that we try to listen. Sometimes there are issues that are too difficult to do something about, but this one was definitely not one of them."

"If customers come in and say, 'I'm trans and actually I want something else, then we'll take the feedback and sort it out."