Regulators attacked European web concert and sports ticket retailers on Thursday, the latest online sector to fall foul of consumer rules.
After airline ticket sales and online electronic goods stores, the middle-men who sell seats and packages for top concerts or football matches are now under investigation, the Europan Commission said.
Traders are now being probed by national consumer standards officials after six out of 10 web retailers were found to be in breach of rules.
Of almost 250 "problem" websites, three quarters gave "incomplete or misleading information about the price," glossing over hidden taxes or handling charges.
Almost as many advertised unfair terms and conditions, with the absence of on-time ticket delivery guarantees or refunds in the event of cancellations.
Nearly half also falsely claimed to be authorised representatives, Brussels underlined.
"The sweeps are working," said EU health and consumer commissioner John Dalli, who cited a sharp rise in compliance among sites selling electronics goods since similar sweep there last year.
Only 16 percent breached guidelines in 2010, whereas more than half were slammed last year.
Launched in May, the operation was carried out in 26 EU member states, plus Norway and Iceland.