The advertising watchdog has clamped down on four of the main secondary ticketing websites by banning their "misleading" pricing information.
The Advertising Standards Authority (ASA) has taken action against StubHub, Viagogo, Seatwave and GetMeIn after finding that they were not upfront and clear with consumers about additional ticket fees and charges that were added at the end of the booking process.
It has banned the websites from not making the total ticket price, VAT-inclusive booking fee and delivery fee clear at the start of the booking process.
The ASA has banned Viagogo from claiming that it is the "official site" after it misleadingly implied it was an official primary ticket outlet rather than a second-hand ticket website.
Viagogo is also banned from making a "100% Guarantee" claim in its ads which the ASA said misleadingly suggested that consumers were guaranteed entry to the relevant venue.
The ASA found there was a reasonable risk that customers could be denied entry with a ticket bought from a secondary site.
UK advertising rules require quoted prices to include non-optional taxes and fees that apply to all or most buyers, and advertisers should also list any applicable delivery fees.
ASA chief executive Guy Parker said: "Many of us will recognise the frustration of being happy with the initial price of tickets on a secondary website only to be stung by hefty fees when we come to book.
"The message from our rulings is simple and it's clear: The price you see at the start should be the price you pay at the end."
A StubHub spokeswoman said: "As a consumer-first ticket marketplace, StubHub supports any measures which make ticket buying easier, more convenient and more transparent for fans.
"We welcome this opportunity to work closely with the ASA and we will be fully compliant with its decision.
"We hope that other players in the ticketing industry, including primary issuers, follow suit."
In November the competition watchdog announced it was taking enforcement action against secondary ticketing websites suspected of breaking consumer law.
The Competition and Markets Authority, which did not identify the sites, had been investigating the market.
A number of artists including Ed Sheeran, Mumford And Sons, Radiohead and Amy Macdonald have encouraged music lovers to stop using Viagogo, GetMeIn, StubHub and Seatwave.
A spokeswoman for Ticketmaster, which owns Seatwave and GetMeIn, said: "Our ticket resale sites already ensure fans know exactly what they will pay at every stage of the buying process, displaying all fees as soon as the customer selects and submits the number of tickets they are looking to buy.
"We will continue to work with both the ASA and the CMA to further develop levels of transparency and consumer protection within the UK ticketing sector."
Alex Neill, Which? managing director of home products and services, said: "It's absolutely right that the ASA has stepped in to prevent secondary ticketing websites from misleading people and potentially leaving them disappointed and out of pocket.
"With people increasingly finding that they have to buy tickets through secondary sites, the sector must be closely scrutinised and action should be taken against companies that aren't playing by the rules."