The competition watchdog has launched a formal probe into the second-hand ticket market amid concerns that consumer protection laws are being broken.
The Competition and Markets Authority's (CMA) "enforcement investigation" will look at seller information, any connections the seller has with the event organisers and whether there are any restrictions on the use of resold tickets which could result in a person being denied access to an event.
Andrea Coscelli, CMA acting chief executive, said: "A night out at a concert or a trip to a big match is something that millions of people look forward to.
"So it's important they know who they are buying from and whether there are any restrictions that could stop them using the ticket."
"It is essential that those consumers who buy tickets from the secondary market are made aware if there is a risk that they will be turned away at the door."
The probe will also take into account where a seat is located in the venue and consider whether both businesses selling tickets and the secondary ticketing platforms advertising them are failing to provide the full range of information.
"If we find breaches of consumer law, we will take enforcement action," the CMA warned.
Earlier this year, the CMA carried out an initial review of the four main secondary ticketing websites - Get Me In, Seatwave, StubHub and Viagogo - to ensure they improve the information provided about tickets advertised on their sites.
The CMA said on Monday that one website was not fully complying with their undertaking and it is actively pursuing it to ensure obligations are met "in full".