It was the trend that allowed adults to dress like toddlers – and not just in the privacy of their own homes. In one of the most unlikely fashion hits of recent years, Harry Styles, Brad Pitt, Jessie J and Justin Bieber were all spotted sporting onesies.

But this year, high street retailers believe the all-in-one may have finally had its day. Instead they are backing novelty Christmas jumpers to be this season's must-have winter warmer for adults and children alike.

For Sainsbury's, which sold a Christmas jumper every 22 seconds last year, this year is all about items from bobble hats shaped like Christmas trees to pudding-tipped mittens. The grocer's buyers have put in orders for five times as many as they stocked last year. Adults will be offered a similar array.

But it means the onesie is likely to be consigned to fashion history, as James Brown, Sainsbury's non-food trading director, said: "We don't really see growth this year in onesies."

He believes adults will be switching from the outsized babygrows to what could be termed the twosie – festive-themed outfits that sit somewhere between pyjamas and a tracksuit. "It will be more about the two-piece and outfits that match head to toe," he said. "Last year we had a Christmas pudding hat which sold out in a week. This year we'll be selling socks, headbands, handbags and hats with bells on."

Asda said it was also favouring novelty accessories over the onesie. "I think the onesie has probably had its day," said a spokeswoman. The supermarket has slightly reduced its range but, by contrast, is increasing its range of jumpers by 62%. "We are going after Christmas jumpers for all the family: Mum, Dad, the kids and the dog," the spokeswoman said.

Retail insiders said the industry was nervous about how it was going to replace the onesie craze, which was popular with all ages.

Clare Varga, head of youth, active and kidswear at trends agency WGSN, said: "I think the onesie is past its peak but a lot of the originators of the trend are looking for an evolution." Like Brown, she is expecting sport-influenced two-pieces with a more clever interpretation of kitsch to be popular with teenagers.

She added: "The whole novelty thing hasn't gone away. It has become standard and the more outrageous these items are the better. That's become part and parcel of the high street's seasonal offering."

The soaring popularity of festive outfits has not only been driven by celebrities, from Styles to Phillip Schofield, but by school and workplace charity events such as Save the Children's Christmas Jumper Day in December.

"Christmas novelty is becoming an event in the same way as Halloween," said John Carolan, Sainsbury's kidswear boss. "So many children now have Christmas jumper day or 'dress as you like' day ahead of Christmas that the most important thing is what they are looking for. There's also a really fun thing happening where people are dressing up in outfits to take pictures for their Christmas cards."

It's not just clothing that is reflecting the UK's new taste for kitsch. M&S has a Christmas cake trimmed with LED lights and is promoting a "gold G&T" – a gin infused with tea that contains gold flakes. Lidl is offering reindeer carpaccio among this year's luxury foods while glitter and sparkles are expected to feature on supermarket shelves as much as they did last year.

But with sales of groceries rising at their slowest rate in almost a decade, supermarkets are looking to clothing as an alternative source of growth. Sainsbury's began testing an online clothing store last week in the Midlands. In stores, the retailer is seeing double-digit increases in clothing sales after it moved to introduce fresh ranges of clothing more often.

The supermarket says it is now the UK's 7th largest clothes and footwear retailer by volume, up from 15th just last year, while it is 11th in terms of value. Even Lidl, the fast-growing German discounter, has turned to clothing. It began selling unbranded fashionable jeans, boots and shirts in stores last month.

• This article has been amended to clarify Sainsbury's market position in terms of value and volume.