Once upon a time, the idea of secondhand baby clothes conjured up images of yellowing vests, worn-out trousers and romper suits with a variety of mysterious stains. But with designer children’s clothes now one of fashion’s fastest-growing markets, the world of infantwear - both new and pre-loved – has had something of a makeover.

There’s no reason why parents who love a label shouldn’t also love a bargain – so when Wavey Garms, one of the most influential secondhand fashion sites in the UK, last week announced the launch of a secondhand designer children’s range, the reaction was enthusiastic.

“My obsession with used kids’ designer clothing came about when one of my friends had a baby and I was looking online to get her something. I found you can pick up some gems really cheap,” said Rhiannon Barry, co-founder of the site, which launched in 2013.

We are all starting to think about the impact of fast fashion, especially with kids’ clothes, which they outgrow so fast Lucy Walford, Littlest Luxuries

Barry noticed a “huge market” for secondhand designer children’s items at affordable prices. “New designer clothes are outrageously overpriced. You could spend hundreds on a coat and it will no longer fit your child in a few months’ time.”

Designer childrenswear is thriving. In January, luxury online retailer Mytheresa expanded into childrenswear, with names including Balenciaga and Dolce & Gabbana. Prices vary but a Gucci jacket retails for £1,740. By contrast, a Ralph Lauren jacket from secondhand online retailer Loopster is just £33.

Loopster started trading used childrenswear 17 months ago, but says it has seen a 23% jump in customers from last December to February this year. “Our bestselling brands retain their quality and our customers love to snap them up at a quarter of the retail price,” said founder Jane Fellner.

Lucy Walford, of used childrenswear site Littlest Luxuries, thinks the stigma around secondhand clothing is disappearing.

“I’m amazed at the sales we’ve had,” she said. “We are all starting to think about the impact of fast fashion, especially with kids’ clothes that are worn for a fraction of time before they’ve outgrown them.”

A baby’s secondhand designer jacket can be a quarter of the original price

Parents often say they do not mind a little wear and tear, but many find that the expensive clothes on offer have been treated as outfits for special occasions, and worn just a handful of times. “I like classic designs like Baby Dior and I get satisfaction from not having paid the full retail price,” said Francesca Williams, who has a six-month-old daughter. For her, it is about dressing her baby the same way she dresses herself.

At Wavey Garms, school sportswear and brands such as Moschino, Burberry and Versace are the most in demand. “Our customers are likely to be someone who grew up in the noughties wearing these brands but wouldn’t have the balls to wear them anymore,” says Barry.

Although social media enables parents to buy secondhand, or make money from selling baby clothes, it can also put pressure on families. “Mums feel the need to showcase images of children looking perfect, and designer clothes are part of this,” says Prof Caroline Gatrell at Liverpool University’s management school. “It adds to the huge pressure on today’s mothers to give the impression that they are leading the perfect family life.”

For many parents, this subculture has always been around – but social media enabled it to enter the mainstream. Jonathan Green, a father of three, says that, in the late 1990s when dial-up internet was awful, newsgroups and eBay were the place to look. “I think we got internet in 1997 and pre-global web access you could get lots of bargains and rarities online. When my daughter was a baby I bought her some lovely clothes”, he says. “And a lot of Kenzo.”