Viagogo and StubHub have had their offices raided as part of an investigation into alleged breaches of consumer law in the secondary ticketing market, the Guardian reports.

Officials from the Competition and Markets Authority acted after reportedly obtaining information in relation to the activities of ticket touts who snap up tickets for in-demand events and then sell them at inflated prices on the two sites.

The searches are part of the CMA’s enforcement investigation into suspected breaches of consumer protection law in the online secondary tickets market. It was launched last year to highlight whether resale sites were providing fans with enough information about their tickets.

It is also looking into whether resale websites give priority to touts they are “connected” to, putting genuine fans at a disadvantage.

The report said that sites such as GetMeIn and Seatwave had cooperated with the investigation.

The data found at StubHub’s office on Tottenham Court Road in London reveals its “top seller” programme, which reportedly manages its relationships with industrial-scale ticket touts selling tickets at vast mark-ups.

According to StubHub’s Top Seller Handbook, touts who make more than $250,000 of sales per year are entitled to benefits including discounts on seller fees, which increase as their sales rise.

Top sellers can also get access to a password-protected web platform, where they can access tools to help them manage their listings on multiple sites and upload dozens of tickets at a time for sale.

StubHub said its Top Seller programme was designed to “incentivise trusted sellers to sell their inventory on our platform, including lower fees and technical support”.

It said the programme followed all relevant laws and eliminated “fraudulent or illegal activity on our site.”