Ed Sheeran's tour producer has said there is absolute collusion over how online sites are getting hold of tickets.
Sheeran's music tour producer Stuart Galbraith was speaking today to British MPs about how to tackle touts.
MPs said they were "horrified" that tickets for Sheeran's gig with the Teenage Cancer Trust were on Viagogo.
Sheeran's manager, Stuart Camp, said tickets for the charity event which should cost between £40 and £110 were on Viagogo for more than £5,000.
The committee heard that adverts for tickets for another Sheeran gig were on secondary ticketing sites within 10 minutes of the singer's O2 show being announced.
"We wrote to the main four secondary sites ... asking them not to list the show, informing them that, as part of our terms and conditions of the show, resale was not allowed ... and that if we were able to find anyone who purchased tickets in the secondary market they would not be allowed admittance to the show," Stuart Galbraith said.
"All four sites ignored our requests and all four listed tickets at inflated prices knowing that it's our intention to cancel those tickets."