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Rihanna's Savage X Fenty lingerie company has been accused of "deceptive marketing". Customers accuse the company of signing customers up to a monthly subscription service "without clearly" disclosing all the terms and conditions.

A complaint has been filed with the Federal Trade Commission and the California District Attorney's office for Santa Cruz County by non-profit watchdog group Truth in Advertising (TINA), WENN.com reports.

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The group alleged Savage X Fenty has been trying to dupe customers by promoting discounts that can only be used once they sign up for the $49.95-a-month VIP subscription.

"It deceptively promotes discounts and product prices that are only available to consumers who are bound to the company's membership program without clearly and conspicuously disclosing this fact in its marketing materials," TINA stated in its complaint.

The watchdog group discovered that when customers use the Savage x Fenty online shop, the VIP membership is automatically added when a customer adds something to the shopping basket.

However, the monthly recurring fee isn't included in the total amount. Shoppers are only made aware of the fee in the site's small print during the checkout process.

Customers have to know to remove the monthly membership from their carts so they can see the normal price of items.

"By default, the company enrolls consumers into a negative option offer known as the Xtra VIP Membership without clearly and conspicuously disclosing all the material terms and conditions, such as needing to take affirmative action every month to avoid recurring monthly charges," the complaint continued.

Emma Tully, a spokesperson for Savage x Fenty, responded via email to CNN business:

"These accusations are false and based on misconceptions of our business. We are proud of our flexible membership program because it allows us to offer unparalleled quality and value to our customers.

"We believe strongly in transparency, which is why we provide multiple disclosures of membership terms throughout the shopping experience, within advertisements, and through our ambassador engagement policies."