Music and sports fans have been warned that tickets bought from touts on auction websites such as eBay may be invalidated.
Leading ticket selling agency Ticketmaster has threatened the action because, it says, genuine fans cannot get tickets for some events due to the activities of unauthorised touts seeking exorbitant prices.
eBay yesterday responded to Ticketmaster's remarks by insisting its site was a safe and transparent place to buy all kinds of tickets. Sellers are required to make the face value of a resold ticket clear to the consumer, it pointed out.
However, it warned buyers to read their contracts carefully and to examine the reputation of sellers before buying any tickets. It also warned sellers they could face action from third parties by listing items in violation of contractual obligations.
Ticketmaster also criticised sites such as needaticket.net, which invites fans to sell tickets so that these could then be resold at "hugely inflated" prices.
Needaticket is currently selling tickets for indie rock group Arcade Fire's concert for €180 and Ireland's soccer international against the Czech Republic for €150.
"We are becomingly increasingly concerned about genuine fans being ripped off by online touts when they buy from unauthorised resellers," said Éamonn O'Connor, managing director of Ticketmaster in Ireland.
He also claimed that some websites advertised tickets for concerts that don't exist. "We will examine as best as possible the tickets put on sale on these websites and, where possible, will work closely with promoters and venues to invalidate those tickets. This means that the purchasers will suffer the embarrassment of being refused entry to a concert, a football game or other event."