The advertising watchdog has referred secondary ticketing website Viagogo to Trading Standards for its failure to make changes to misleading pricing information on its website.

The Advertising Standards Authority (ASA) said Viagogo was continuing to mislead consumers by not being upfront and clear about additional booking fees and delivery charges added at the end of the booking process.

The Geneva-based firm was one of four who were subject to ASA action in March after a clampdown on “misleading” pricing information.

StubHub, Seatwave and GetMeIn were the other three companies subject to the action against so-called “drip pricing” – where VAT, booking and delivery fees were added at the end of the booking process.

However, the ASA said Viagogo failed to meet its May 29 deadline to make the necessary changes to its website.

It added: “As of today, the ASA is not satisfied that Viagogo has brought its website in line with the advertising rules.

“The ASA made clear to Viagogo that if changes were not made it would consider imposing further sanctions, including referring them to its legal backstop power, National Trading Standards, for consideration of statutory sanctions which can involve prosecution and fines.”

ASA chief executive Guy Parker said: “Viagogo was given clear warning and handed the opportunity to play fair with consumers by removing misleading pricing information from its website; its failure to do so means it will now face the consequences.

“Where an advertiser or business is unwilling or unable to follow the advertising rules, we will act. In light of Viagogo’s inability to get its house in order, we’re referring it to National Trading Standards to consider appropriate action.”

The ASA earlier warned Viagao that it was “breaking UK advertising rules” by failing to make additional fees clear.

Campaign group Fanfair Alliance, who campaigned against secondary ticketing online, and the music promoters Festival Republic and Kilimanjaro Live were among those who complained to the ASA about issues including additional ticket fees.

According to the ASA, Viagogo said “each ticket home page contained the text ‘prices exclude booking and delivery fees (applicable by transaction)’, and therefore at the first stage of the customer journey, consumers were informed that the prices displayed did not include additional booking and delivery fees”.

Digital Minister Margot James told BBC 5 Live Breakfast’s Nicky Campbell: “If there’s one message I could get across to your listeners here this morning, it is that there are four big choices when you can’t get a ticket for an event from the primary seller – and you’ve got to go to a secondary site – there are four choices. Just don’t choose Viagogo, they are the worst.

“I think the best thing is for people to be made aware, we can’t necessarily, especially because they are based outside of the UK, there are limits to what we can do to single them out.

“They will have to comply with the law in the end, it’s just the other three big companies have agreed to do so in advance, but we are taking more steps to constrain the activities of secondary ticketing sites.”

Sharon Hodgson, chairwoman of the All-Party Parliamentary Group on Ticket Abuse, said: “It is not surprising that Viagogo have been found to be breaking UK advertising rules.

“Time and time again we have heard of Viagogo misleading and ripping off genuine fans, yet no real action has been taken against them.

“I welcome the ASA ruling, but hope that finally Viagogo will get the comeuppance they deserve after years of breaking the law.”