Allen, who was snubbed for four gongs at The Brit Awards last week, will help design Lily Loves, a range of clothing for New Look that will include six dresses, two pairs of shoes and a range accessories inspired by her unconventional fashion sense, which often features brightly coloured ball gowns with trainers, large hoop earrings and gold jewellery.
The deal is the latest in a wave of high profile tie-ins with affordable UK high street clothing chains, with Madonna signing a deal for a clothing range with H&M, and Kate Moss set to unveil her Top Shop designs one week before Allen's are due to hit New Look stores.
New Look, founded by millionaire retailer Tom Singh, has diversified its remit in recent years with the aid of creative agency ODD, which masterminded the chain's first major UK ad campaign, to include a limited men's range and an emphasis on its affordable credentials.
A spokeswoman for New Look said: "When [Allen] was breaking last summer, we thought she was very different, and everyone was picking up on her style, particularly the big prom dresses. It's perfect timing, as we're selling a colossal amount of dresses."
The deal coincides with the continued success of Allen, who has been making some headway in the US charts, with her singles 'LDN' and 'Smile' being rotated heavily on college radio stations.
Allen chose to make her debut album, 'Alright, Still', which went to number one in the UK charts in July, available on her MySpace prior to its release, helping her garner a substantial word of mouth before it was officially released.