When it comes to dressing for a party, a T-shirt is usually something you change out of rather than put on.

But this party season, the casual tee is experiencing a metamorphosis. Enter: the cocktail T-shirt.

Made of wool rather than cotton, it typically features a roomy rather than a clingy cut and sleeves that hit just above the elbow. Sometimes it comes with glistening embellishment around the neckline or it is plain, giving the wearer the option to add their own level of glitz with a sparkly necklace or brooch.

“They have that sort of understated look that a T-shirt tends to give the wearer, but unlike the way a cotton T-shirt sort of unravels by midday, the knit has a more polished effect,” says Buffy Reid, the founder of the British knitwear brand &Daughter. She describes the item as having “the same ease as a T-shirt but the elegance of a knit”.

The cocktail T-shirt is an emerging category in evening knitwear. As a natural fibre, wool has thermodynamic properties, meaning it will keep you warm in cool weather and cool in hot conditions – a quality ideal for the festive season where one person’s central heating level is another person’s sauna.

&Daughter’s evening knitwear offerings include a slouchy cashmere T-shirt made from cashmere spun in Hawick in Scotland that comes in eight colours, including – a holiday ready red, and a bestselling pickle green lambswool iteration with slightly voluminous sleeves.

Miuccia Prada, known as Mrs Prada in the fashion industry, is one of the main catalysts behind the humble T-shirt’s glow-up. She consistently wears a simple cashmere jumper with the sleeves pushed up and a gem-set necklace for her post-show bow.

This season she and her co-designer, Raf Simons, toyed with the idea of femininity and beauty on the catwalk, declaring it “is not a time for decadence” as they unveiled knitted T-shirts featuring chains and pearls dangling from the neckline, worthy of Mrs Prada’s own wardrobe.

While the Prada T-shirts sell for four figures, the high street has been quick to emulate the look, albeit using synthetic fibres or blended mixes rather than pure wool. This means they won’t biodegrade and as a non-breathable fabric could contribute to sweating. There are also concerns that high demand for cheap cashmere is contributing to desertification in countries including Mongolia, where the goats are farmed.

Queralt Ferrer, John Lewis’s fashion director, says the elevated T-shirt trend is being driven by customers looking for value for money and versatility. Its £80 cashmere T-shirt, which can be worn to the office or to a fancy dinner, has become a bestseller.

Naomi Pike, a commissioning editor at Elle UK, is a fan of the cocktail T-shirt and says it can also help reduce overconsumption. “I like to get good use out of all of my wardrobe and these help that happen when it comes to rotating skirts and not wasting precious pennies on one-hit party wears.”

Pike says the cocktail T-shirt also appeals as it offers an alternative to the flesh-exposing tops typically marketed to shoppers each party season.

“Cashmere, with its soft knit and stretch, fits me and my proportions better as I often find I’m in between sizes in T-shirts as my bust is big, waist small and shoulders narrow. Cashmere stretches better to accommodate these proportions that fashion often punishes,” Pike says.