The advertising watchdog confirmed to "considering" complaints from users who have signed up for the Prime service on Amazon.
According to The Independent, the retail giant is facing complaints about delays in festive deliveries.
Amazon's Prime service costs £79 per year, which includes unlimited one-day delivery, and access to films, music, and television shows.
A spokeswoman for the Advertising Standards Authority confirmed to "considering" complaints but also added that no official investigation had been opened yet.
However, Amazon told one customer that "this is a busy time of year and due to high order volumes, estimated delivery dates can vary." (ANI)