Presented to a select group of designers and fashion editors during New York Fashion Week, the 34-year-old's ten-dress collection - which echo some of her own wardrobe favourites - has garnered positive reviews.
In addition to being praised for their beautiful silhouettes, the designs have made headlines with their attention to detail and wearability. Lightweight internal corsetry and clever seams make sure everything stays in place, while grosgrain-ribbon lines the waist for comfort.
Made in luxury fabrics across a subdued palette of black, navy, cream and cobalt, the slender-fitting dresses - which go on sale in February - will retail for between £600 and £1,900.
Although Posh admits to having a little help from designer pal Roland Mouret in putting together her London-based team of four, she designed the collection on her own, basing it on her favourite styles and designers. The mum-of-three spent hours working on prototypes at home in LA and e-mailing patterns across to Britain.
"I've been working on this for 34 years," she says. "I always wanted to be a fashion designer."