Auto Trader has warned customers against a third-party website that has been taking payments to sell their cars on the Auto Trader website.
In a safety and security warning last weekend, the UK's biggest used car classified advertising website said it has already received several complaints from customers who believed the website - Seller-Autotrader - was linked to Auto Trader.
The Seller-Autotrader website is now no longer operating.
Auto Trader also warned that another company is also making fraudulent phone calls, ringing customers claiming to be from Auto Trader and asking for their bank details in relation to the advert they have placed.
Customers are urged to contact Auto Trader's consumer security team if they have queries.