Women in the Royal Air Force have been banned from wearing skirts on parade in an effort to make the service more inclusive, sources say.

The trousers-only rule is believed to have been put in place last year due to an increase in transgender personnel, The Times reports. Feedback from female staff who said marching in skirts is uncomfortable was also reportedly behind the decision.

Women make up about 14 per cent of the RAF's 33,000 personnel, but it isn't known how many are transgender. They have been wearing skirts since World War II, but the RAF wants to ensure it is a "modern and inclusive employer," a source explained to The Sun.

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"We have men who want to live as women, women who want to live as men and personnel who do not identify with any gender," the source added.

"The view was we need a uniform policy to cut through all of that and say there is one uniform for everyone and that's that. It's about including people and encouraging diversity."

Women in the RAF were first allowed to wear trousers on parade after a uniform shake-up in 2001. The change was introduced to give the service a more "modern" image, but the latest decision has received criticism for its "political correctness".

Servicewomen are said to be allowed to wear skirts on other occasions when they aren't marching. According to sources, a decision to make the uniform change has been made, but it hasn't been put into action yet.

"Uniform regulations, including dress for formal parades, are regularly reviewed," a spokesperson said. "No decisions have been made to make any changes."