Oasis and Ticketmaster should refund fans who ultimately paid hundreds of pounds more than the face value of the tickets after prices were driven up through so-called “dynamic pricing”, consumer group Which? said.

Which? called on the band and the ticket company to “do the right thing” and refund the difference between the face value of the tickets and the grossly inflated price that many ended up paying.

Some fans paid more than £350 for tickets with a face value of less than £150 and had to make a split-second decision about whether to complete the purchase as dynamic pricing drove up prices during the booking process.

Lisa Webb, consumer law expert at Which?, said: “It seems hugely unfair that Oasis fans got up early and fought their way through the queues only to find that ticket prices were more than double the original advertised price.

“Oasis and Ticketmaster should do the right thing and refund fans who may have been duped into overpaying for tickets that would have cost half as much just hours earlier.”

Webb added: “Which? believes that Ticketmaster’s ‘on demand’ pricing practices for Oasis tickets may have breached consumer law as fans appear not to have been properly warned of the practice until far too late in the purchasing process, resulting in a nasty shock at the box office.”

Under the rules designed to protect consumers against unfair competition, traders must not display their prices in a misleading manner or omit essential pricing information.

Last week, Oasis blamed promoters, Ticketmaster and the band’s management team, saying they had “no knowledge at any time” of the sales strategy, which is now the subject of separate investigations by the UK and its European antitrust authorities.

A Ticketmaster spokesman said: “We are committed to working with the Competition and Markets Authority and look forward to sharing further facts with them about ticket sales.”

The band’s press office did not respond to a request for comment.

Liam and Noel Gallagher’s reunion tour, announced 15 years after the band’s acrimonious split, is expected to generate revenue of £400 million according to some estimates.

Last week, Oasis announced two more dates at Wembley Stadium, bringing the total number of tours to date to 19. A “special, staggered, invitation-only” draw for tickets to the additional Wembley concerts will not feature dynamic pricing.

The date of the giveaway has not yet been announced, but it will give verified fans who did not receive a ticket in Ticketmaster’s original pre-order giveaway another chance.

All ticket buyers – up to 180,000 tickets are available for the two nights in Britain’s largest venue – were contacted last weekend.

Prices have not yet been released, but before the initial vote on advance sales, organisers said standing tickets would cost around £150, while standard seated tickets would cost between £73 and around £205.