George Osborne and Ed Balls read out a “misleading” advert for the controversial ticket resale website Viagogo during an episode of their podcast, the advertising regulator has ruled.

The two men, who put aside their past rivalry at the dispatch box to launch a podcast in 2023, espoused the benefits of the “secondary” ticketing site in a promotion during an episode broadcast in April last year.

Balls, a former Labour shadow chancellor, told listeners that “over half the events listed on Viagogo had tickets selling below face value”.

Osborne, a former Conservative chancellor, said: “It sounds like Viagogo might be the solution next time I need cheaper tickets to the hottest shows in town.”

Viagogo and rivals such as StubHub allow professional “traders” – defined as those selling more than 100 tickets a year – to make huge profits by hoovering up seats at gigs by acts such as Oasis and Ed Sheeran and selling them on for massive mark-ups.

The government is considering banning for-profit resale, following repeated claims that fans are being exploited.

On Wednesday, the Advertising Standards Authority (ASA) said that Viagogo, which has previously been hit with a court order from the Competition and Markets Authority (CMA) for flouting consumer laws, had misled the public with its claim about the volume of events for which tickets were sold below face value. It said the promotion breached the advertising code and should not appear again.

The script of the advert was based on Viagogo’s internal calculation that 53% of concert listings on the site included at least one ticket listed at below face value. The ASA said fans would have understood the claim to mean more than one lower-priced ticket was available for those events.

It said: “One ticket per event was not a significant proportion of tickets and, as such, did not represent a reasonable chance for consumers to purchase tickets below face value … we considered that the claim, as it would be understood by consumers, had not been substantiated and was therefore misleading.”

It also took issue with the definition of face value that Viagogo applied, which included the application of 20% extra for fees, which it said differed from the one widely understood by consumers and also the definition the company used on its own website.

The music industry group FanFair Alliance, which campaigns against for-profit resale and touting, submitted the initial complaint to the ASA. It said Viagogo’s claim was “laughable”.

A FanFair spokesperson said: “According to a report by the CMA, 80-100% of the tickets sold through Viagogo in 2019 were priced at more than 20% above face value. It is a website dependent upon large-scale ticket touts.”

A Viagogo spokesperson said: “The advertisement in question is from last year, has been discontinued and has not aired since then.” They added that Viagogo was “fully compliant in the UK”.

The podcasting firm Acast is responsible for adverts on the Political Currency show hosted by Osborne and Balls, according to Persephonica, which makes the programme.

The Guardian has approached Acast for comment.