Casual fashion firm American Apparel is expanding its kids' and babies' clothing lines by 'shrinking down' some of its signature adults' styles into smaller sizes.

The Los Angeles based firm says the move follows requests from customers, and says the new lines will include gingham button-down shirts, suspenders, high-waist skirts and several styles of print leggings.

"We've been looking forward to building this part of our line and are very happy to have answered this demand," said Marsha Brady, a creative director for American Apparel.

"Our adult styles are pieces that people buy over and over again and we want that to be true for kids clothing as well."

As well as translating dozens of its adult styles for the children's lines, the firm has also incorporated new colours and designs, which will add an extra 30 pieces to the range.

American Apparel currently sells its kids and baby lines at more than 70 US retail locations, several international shops, and online from its e-commerce site.

The lines are all knit, cut, designed, sewn and marketed in downtown Los Angeles at the company's vertically integrated facilities.