The company's website said Ticketmaster Platinum "offers fans the best available tickets for an event direct from the artist".
It added that the goal of the service was to give fans "fair and safe access to the best available tickets, while enabling artists and other people involved in staging live events to price tickets closer to their true value."
Three people complained that the claim that the tickets were "the best available" was misleading and unsubstantiated.
Ticketmaster said it did not believe consumers were likely to interpret the claim to mean they would be buying the best tickets that had ever been sold for that event.
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They said that many of the most popular events sold out quickly when tickets first went on sale to the public, and the Platinum product enabled organisers to sell a small proportion of the most sought after tickets at market rates that reflected demand.
As a result, Platinum tickets did not sell out as fast as standard tickets, allowing customers to continue to buy them up until much closer to the time of the event.
Ticketmaster said the proportion of Platinum tickets was never more than 9% of total tickets.
However, it said there might come a point where Platinum allocations for certain events comprised "the better and best" tickets, rather than just the "best" tickets for the event, and had therefore begun to describe them as "in-demand" tickets instead.
The Advertising Standards Authority said consumers were likely to interpret the "best available" claim to mean that those tickets were better than any other available tickets for the event.
It said: "In particular, we noted that the claim was unqualified and we also understood that for the seating tickets, there could be Platinum tickets on sale at the same time as general tickets, with no discernible difference between the two in terms of customer experience."
However, it found that Platinum tickets were likely to be more expensive than the general tickets, and that Platinum standing tickets were only released for sale after the general standing tickets were sold out.
The ASA said: "We therefore considered that whilst the Platinum tickets were among some of the best seats at the venue, they did not offer a tangible benefit compared to some of the general seating tickets and the experience offered by the Platinum tickets was no better than the experience offered by some of the general tickets.
"We also considered that in the case of some Platinum tickets, the experience offered, when viewed objectively, was worse than the experience offered by some of the general tickets, because they were further from the stage or did not offer as good a view of the stage.
"Because of that, we concluded that the claim that the Platinum tickets were 'the best available tickets' had not been substantiated and was misleading.
"We welcomed Ticketmaster's changes to their advertising."
A Ticketmaster spokeswoman said: "Platinum is one of the solutions Ticketmaster developed for artists and event organisers to get tickets, which are priced dynamically in some of the most in-demand areas, directly into the hands of fans.
"We constantly strive to be transparent and clear with the consumer. The wording in question on our website was changed over a year ago."