Analysis found listings for tickets for artists such as Adele and Coldplay did not include any details of sellers
StubHub has been accused of failing to disclose when customers are buying tickets from professional touts, in breach of a legal undertaking given to the consumer watchdog.
The Competition and Markets Authority (CMA) requires sites such as Viagogo and StubHub to let customers know when tickets are being sold by professional ticket traders, who dominate resale listings for gigs and other events, leading to fans paying massively inflated prices.