The lingerie range has been designed for "every shape" and includes bodices, 50s style knickers, lace sets and "playful babydolls".
Klass claims the collection is aimed at making women "feel comfortable, glamorous and most importantly, confident".
Littlewoods unveiled Klass as its style ambassador in July. It has already commissioned her to create two clothing ranges and is using her to front its advertising campaigns.
The brand’s £2.3m autumn campaign launched this week and features Klass moving through a "magical playground" filled with women playing on retro-looking rides.
Littlewoods claims the dress that Myleene designed and wears in the ad has gone on to become its "first ever social media sell-out".
The brand promoted the dress on Twitter and Facebook on Tuesday (25 September) and sold out of the initial allocation before the TV ad was aired the following day.
Littlewoods is following in the footsteps of Marks & Spencer (M&S), which launched a lingerie range designed by Rosie Hungtington-Whiteley after picking her to front its advertising for its Autograph range.