Oxfam's annual "Second hand September'' campaign will be fronted by actress Sienna Miller.
The campaign, which will raise awareness about the effect fast fashion has on the planet, comes ahead of the UN climate summit COP26, which takes place in Glasgow in November.
Consumers send 13 million items of clothing a week to landfill sites and the textile industry accounts for up to 10% of the world's greenhouse gas emissions. To help reduce emissions, Oxfam is asking consumers to buy only second-hand clothes for the month of September and donate their pre-loved items.
Miller will feature on posters in the windows of more than 500 Oxfam shops dressed in Oxfam clothes, which will be available to buy in Oxfam's pop-up shop in Selfridges, London. Shoppers can raise awareness by sharing their one-of-a-kind finds using #SecondHandSeptember and tagging @OxfamGB.
The Oxfam Selfridges pop-up shop, styled by Oxfam's independent fashion advisor Bay Garnett, celebrates vintage treasures such as heritage tweed and sheepskin coats. Garments that evoke nostalgia for the 1980s, including punk-inspired clothes and velvet dresses also feature, alongside some of the garments Miller is modelling. Illustrator James Lacey, of Pointless Illustrations, has designed a T-shirt which will be on sale in-store.
The pop-up shop runs from 6 September until the end of December and the money raised will go to Oxfam.
People can also support "Second hand September" by shopping on the Oxfam Online Shop or by finding their local store using the online shop finder tool.
Danny Sriskandarajah, chief executive of Oxfam GB, said: "The climate crisis is already wreaking havoc on people's lives with extreme weather events that are destroying homes and harvests. Scientists warn we have just nine years to prevent catastrophic global temperature rises so all of us – governments, companies and individuals – have a role to play in rapidly reducing carbon emissions.
"Choosing second-hand is one way we can leave a lighter footprint on the planet while sending a message to retailers that we want them to slow down fashion. By shopping at Oxfam, you're also raising money to help some of the world's poorest people cope with the impacts of climate change."