Gardai have warned people not to buy tickets for the second Robbie Williams concert from touts outside the Lansdowne Road venue tonight.
"If you come up to the gate with a forged ticket, you've paid your money for nothing and probably paid well over the odds. You won't be getting in," a spokesman said.
Meanwhile, the National Youth Council of Ireland (NYCI) has criticised the Government for not clamping down on ticket touts as the summer concert season approached.
The NYCI spokesman, Mr Colm O Mongain, said he was disappointed that a Bill, currently being considered by the Joint Committee on Tourism, Sport and Recreation, had not become law before the Dail went into summer recess.
"The exploitation of concert and match-goers by unscrupulous ticket touts cannot continue unchecked," he said.
"Ticket-touting preys on the dedication of fans in a cynical fashion and cannot continue. Action is needed as soon as possible."
Mr O Mongain said the problem particularly affected younger fans, who were either priced out of attending events or encouraged to make excessive financial demands on their parents.
Recent events such as the sale of tickets for U2's Slane concert this summer, as well as annual events such as the All-Ireland football and hurling matches, would see young fans paying at least twice the normal price for tickets.
New methods of buying tickets in bulk had also hit younger fans, many of whom did not have access to the Internet or credit cards, he said.
"The most recent example of this was the sale of 80,000 U2 tickets in under an hour, resulting in angry scenes outside ticket outlets as queueing fans found that their long wait had been in vain," he said.
"This has exacerbated the touting situation as some people buying multiple tickets by credit card sold them on at an exorbitant price."
Young people often had no choice but to attempt to obtain tickets from touts outside venues.
"It's unfortunate coming up to summer that something couldn't be put through with all the upcoming events," he said.
"Preventive measures need to be put in place rather than bolting the door after the horse has fled."
