Fashion is becoming increasingly disposable for Australians, with almost a quarter of people admitting to throwing out clothes after just one wear, a study has found. And four out of 10 people surveyed by YouGov said they had put unwanted fashion items in the bin, rather than trying to repair or recycle them.

As Australian fast-fashion booms to an industry worth $2bn a year, the YouGov report found that 75% of Australian adults have thrown clothes away in the past year; 30% tossed more than 10 garments.

The throwaway culture is creating a serious environmental problem, with 24% saying they threw out a garment after one wear. One in six people binned at least three garments they’d worn only once.

The report also showed a generational divide in attitudes towards clothing. Millennials enjoy buying new clothes, with almost one in four saying they had purchased at least half the clothes they own in the past year. They are also more likely to throw out their clothes within two years.

Baby boomers are the opposite. More than two-thirds said that less than 10% of the clothes they own had been purchased in the past year.

When it comes to getting rid of unwanted items, boomers are more likely than millennials to give their clothes to charity (86% v 69%) or recycle them (26% v 20%). Younger shoppers are more likely to sell them online or – worryingly – burn them.

For everyone, the most common reason for turfing items is because they no longer fit or are damaged. But millennials are more likely to toss items because they are sick of wearing them (24%), they have become unfashionable (19%) or are more than a few seasons old (18%).

Fashion Revolution’s coordinator, Melinda Tually, says she’s not surprised by the findings or the generational gap in attitudes, because the definition of value has shifted.

“Older generations grew up considering what value is – which is longevity and high-quality materials and something you could keep season after season,” she says.

“Now for millennials growing up, cheap fashion to them is the definition of value. If you can get a T-shirt for under $10, that’s value.”

She says the low cost and easy accessibility of fast fashion has made it easier to discard things: “The sense of this [item] is always going to have some inherent use, I think, has been lost when things are so easy to come by.”

Australia’s fast-fashion industry is booming and has grown 21% in the past five years, an Ibis World report found. Where once fashion customers waited for an overseas trip to stock up on cheap clothes, retailers including H&M, Uniqlo, Zara and Topshop/Topman have arrived and are expanding rapidly (albeit with some hiccups) in the market.

Online fashion shopping is also part of the problem. An Australia Post report showed 22% of online purchases were fashion items, with significant growth for three years running. Australian households received an average of 3.2 parcels of fashion items in 2016. Anecdotally the busiest time for fashion sales on The Iconic website is on a Thursday, for delivery on Friday, which suggests shoppers are looking for something new to wear at the weekend, with little consideration of its long-term use.

So customers are getting their fashion fix fast – but then they’re binning it. And the increasingly disposable nature of fashion is causing huge problems for the environment, with more than 500,000 tonnes of textiles and leather sent to landfill in Australia alone.

A sustainability consultant, Jane Miliburn, who has just launched her book Slow Fashion, has found that Australians buy an average of 27kg of textiles each year (including leather and homewares) and then discard 23kg into landfill, mostly synthetic fibres. So the amount of textiles Australians consume annually is double the global average of 13kg a person.

There are a few streams to landfill, she says, not least the fact that 25% of what charities receive ends up there. “Op shops are overwhelmed with donations and, if there is any mark or problem with it, it just goes straight into their landfill pile,” she says.

Fast fashion is pushing all prices down to the bare minimum, which is bad news for those who depend on the industry for their wages. An Oxfam report found that just 4% of the amount Australians spend on clothing goes to the garment workers.

There are ways to fix the problem, says Melinda Tually, if everyone plays their part. Councils and local government could encourage more people to recycle unwanted items by returning many of the charity bins which have been removed from car parks owing to illegal dumping. “Accessibility is key,” she says.

Retailers could do better, such as offering more take-back schemes. The Swedish fashion brand H&M encourages customers to return all unwanted garments, which can be sold on as secondhand items, converted into other products or turned into textile fibres. Similarly the outdoor wear company Patagonia offers free repairs and recycling to all customers. “There is a role for brands to recognise that their responsibility doesn’t stop at the till,” Tually says.

And consumers should know better than to bin things unnecessarily. “We know that over 95% of textiles in landfill are reusable so there’s really no need for any of it to be there,” Tually says. “Consumers have that responsibility to know that you are throwing loads of resources away that will never be able to be recouped.”

Finally, shoppers need to consider whether they should snap up yet another so-called bargain. “It’s the impulse shopping that leads to an increase in dumping, more so than considered purchases. So slow down and think about things properly so they don’t end up in the bin.”