Ariana Grande Photo: IC

 US pop star Ariana Grande has sued fashion retailer Forever 21 for using her trademark style to promote its products without her permission, including adverts featuring a "look-alike model."

Grande is seeking $10 million over claims the brand, and its spin-off cosmetics line Riley Rose, created an online campaign with striking similarities to her music videos, such as "7 Rings," from late 2018.

The lawsuit, filed in Los Angeles district court Monday, claims the campaign was intended to trick consumers into believing Grande had endorsed Forever 21's youth-oriented products.

"Even a single social media post by Ms Grande can garner fees of several hundred thousand dollars, and her longer-term endorsement arrangements command fees in the millions of dollars," it said.

Grande has 163 million Instagram followers, making her the most-followed woman on the photo- and video-sharing social media platform.

Images from Forever 21's Instagram account cited by the lawsuit showed a model wearing purple camouflage clothing and a pink headband and boots similar to those worn by Grande in the "7 Rings" music video.

The images appear to have been taken down from Forever 21's social media accounts.

A Forever 21 statement denied the allegations, adding that the fashion firm has "worked with [Grande's] licensing company over the past two years."

"We are hopeful that we will find a mutually agreeable resolution and can continue to work together in the future," it added.

Bloomberg News reported last week that Forever 21 was preparing for a bankruptcy filing.