Fans are being charged four times the face value for tickets for this weekend's All-Ireland football quarter-finals.
A double-header takes place at Croke Park tomorrow, as Tyrone face Mayo at 4pm and Dublin take on Donegal at 6pm.
Both fixtures are officially sold out, but tickets are still available on a number of online sites at inflated prices.
The controversial website Seatwave - which is owned by Ticketmaster - has tickets on sale for the Nally Stand priced at €79. The cost is almost 300pc more than the official price of terraced tickets, which are advertised for €20 on the official GAA website.
Barry Fennell, of the Hill 16 Supporters' Club, described the massive inflation in price as "a disgrace". He said that more should be done to clamp down on the re-selling of tickets at higher prices.
"The GAA should be able to do more against this sort of thing," he said.
"hy can't they do more about this? It's terrible for the genuine fans who may not be able to afford such high prices."
Mr Fennell also raised questions over the decision to host a double-header in Croke Park, saying that the wiser move would have been to hold the two lucrative ties on separate dates.
A spokesperson for Seatwave last night told the Herald: "Ticket holders set the price and list their tickets for resale - not Ticketmaster - nor does Ticketmaster divert tickets to this site."
They said Seatwave "acts as a platform for individuals to list their unwanted tickets at a price that they choose".
"It is a ticket marketplace that responds to what fans want - the ability to buy and resell tickets when tickets are no longer available on the primary market, or when ticket-holders can no longer use their tickets," the spokesperson said.
"Seatwave offers a 100pc money-back guarantee to the ticket purchaser as a layer of consumer protection, but will not protect sellers that attempt to sell tickets fraudulently."
Meanwhile, the GAA have unveiled new plans to reform the All-Ireland football championship, with the proposed introduction of a 'super league' for the quarter-final stages.
Under the terms of the proposal the last eight teams would split into two groups of four and play against each other over three weekends.
It would involve the addition of eight extra games to the championship calendar and is dependent on revisiting the playing of extra-time, if needed, in all championship matches - except the All-Ireland final.
The proposed format would see the provincial championships and four rounds of qualifiers played as normall.