In a project called Le Lab, designers will showcase their collections to customers, who will vote for their favourite.
The winning designs will go on to be sold through BrandAlley.co.uk, which has eight million subscribers in the UK and France.
Melissa Littler, marketing director for BrandAlley, said: "This is an innovative way to shop within an online community, where it is the customer and not us, who decides what will go on sale.
"It is also a great opportunity to break through for young, emerging fashion talent, who will also be able to learn from, and be influenced by, their future customer."
The idea grew out of BrandAlley's campaign to find the perfect Little Black Dress, last year.
Littler said: "The Little Black Dress trial has proved that this is something our customers are really excited by.
"Letting your customers make the decision on what to sell is something I believe will become more and more prevalent in today’s online, social network-dominated marketplace."
Each month, designers will pitch their proposals for a piece of clothing, such as a perfect summer t-shirt, summer dress or trenchcoat.
Successful pieces will sell on Le Lab with a 50% discount, before entering the BrandAlley catalogue.
The fashion sector is becoming increasingly competitive. Fashion price comparison site stylecompare.co.uk launched yesterday (10 February), while Ebay and Facebook have both launched e-shops, attracting brands such as Superdry, French Connection and ASOS.
BrandAlley was launched in the UK in 2008 as a joint venture between the highly successful French enterprise and News International.