Four major ticket resale websites have been ordered to stop "misleading" fans by failing to come clean about fees in their advertised prices.
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.
Such fees can add significant costs onto the upfront price of a ticket.
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."
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.
The ASA has banned Viagogo from claiming that it is the "official site" - wrongly implying it was an official ticket outlet for venues rather than a second-hand ticket website.
Viagogo is also banned from making a "100% Guarantee" claim in its adverts, after the ASA found they were misleadingly suggesting 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.
A number of artists including Ed Sheeran, Mumford And Sons, Radiohead and Amy Macdonald have encouraged music lovers to stop using secondary ticketing sites.
Mumford and Sons' Winston Marshall and Ben Lovett hailed the crackdown as a "great improvement" that would improve transparency.
In November the Competition and Markets Authority announced it was taking enforcement action against a number of secondary ticketing websites suspected of breaking consumer law.
Alex Neill, managing director of home products and services at consumer magazine Which?, welcomed the action.
He 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."
A spokesman for StubHub said they accepted the decision and would work to become "fully compliant".
He added: "We hope that other players in the ticketing industry, including primary issuers, follow suit."
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."