Britney Spears and Justin Timberlake in denim
Britney Spears and Justin Timberlake's double denim look is iconic - but did these outfits end up in the washing basket? LUCY NICHOLSON/AFP/Getty Images

How often do you wash your jeans? After every wear? When there are too many weird food stains to ignore? Never?

It's a question that seems to arise online from time to time and Twitter users recently tackled the topic by detailing their jean washing habits (or lack of).

But who is right? As high-quality denim can last for decades, surely a pair of jeans need to see the inside of a washing machine at least once?

The answer depends on who you ask, how you want your jeans to look, and what you plan to do in them.

The debate comes down to the fact that authentic jeans are made of raw denim, meaning the fabric is not processed, according to the Guardian. The way a person wears them - from scrapes against a wall to how they bend their legs as they sit - gives the material a unique character.

Sticking them in the washing machine breaks down the fibres, cleans away the deep indigo colour and the characteristic stiffness of the fabric.

It was reported in 2014 that Chip Bergh, the CEO of Levi's, put the question to bed by declaring that he never washed his jeans. He later explained he was making a point about sustainability as cleaning clothes unnecessarily wastes water.

Bergh said he wanted to "challenge the mindset that we need to throw everything into the washing machine after one or two wearings".

He had owned those particular jeans for a year, he said, and normally wore them in the office.

"Don't wash your jeans, or significantly reduce your frequency of washing," he wrote in a piece entitled The Dirty Jeans Manifesto.

"Or, you can do what I do, and simply spot-clean your jeans if they aren't a total mess. And, when my jeans really need a wash, I do it the old fashioned way: I hand-wash them and hang-dry them. Ask my wife – I really do!"

Denim blog Heddels said that there was "really no right time or wrong time to wash your jeans. Raw denim is a personal journey that only you know when the right time is for your favourite pair of pants to take the plunge".

There are a few exceptions: when the dirt becomes embedded and starts to break down the fabric; if the jeans are damp and therefore likely to be infested with mildew; when you can smell them at arm's length, and, er, if a person "crapped their pants". Um, thanks for the tip guys.