The Minister for Tourism and Sport has announced a non-statutory inquiry into the Olympic ticketing controversy.
Following a meeting with the Attorney General Máire Whelan, Shane Ross said it would be chaired by a retired judge who will be appointed next week.
The Minister said the terms of reference would be finalised shortly thereafter and he hoped it could complete its work in 12 weeks.
Mr Ross said he had discussed the issue with the Taoiseach who is fully supportive - as is the Attorney General.
But the judge will have to get answers without the power to compel witnesses because this is a non-statutory inquiry.
A joint statement was issued on behalf of Mr Ross and Minister of State Patrick O'Donovan this afternoon.
"We believe that a judge-led, non-statutory inquiry is the most appropriate mechanism to establish the facts," said the statement.
Mr O'Donovan said this inquiry will not affect any investigations that are under way in Brazil.
Earlier, the Olympic Council of Ireland (OCI) said it will "co-operate fully with any State inquiry into its handling of ticketing arrangements for the Rio Olympics".
In a statement, it said: "The OCI will now also commission its own independent inquiry into the ticketing arrangements for Rio 2016."
It said its previously announced internal inquiry has been "discontinued".
Meanwhile, two ticket agencies - THG Sports and Pro 10 - said they would also co-operate fully with an inquiry into the sale of Olympic tickets in Rio.
THG Sports issued a statement this morning calling for an independent inquiry into the affair.
It said it would fully co-operate with such an inquiry as it said it "can demonstrate that the company has acted lawfully at all times".
THG also said it "believed that a full and proper judicial assessment cannot be achieved without consideration of, and access to, all the THG compliance documentation which THG has followed in the provision of hospitality packages in Rio."
THG is owned by Marcus Evans Group, which also controls English football club Ipswich Town.
In 2010, the Olympic Council of Ireland appointed THG as its official ticketing agent for the 2012 London Olympics and the 2014 Winter Games in Sochi.
THG did not have a permit to sell Irish Olympic tickets for the Rio Games.
The Authorised Irish Ticket Reseller, Pro 10 Sports Management, also issued a statement saying it supports the call for a judge-led inquiry.
It added: "A Commission of Investigation should be established speedily; investigate all relevant facts and report its conclusions in the shortest possible time. We understand that the terms of any investigation should respect the Brazilian legal process."
Pro 10 said it is "anxious that the full facts are established and made public as soon as possible so that our good name can be exonerated".
It has previously said that Mr Mallon was holding the tickets at the centre of the controversy for collection from its clients.
In an email, seen by RTÉ News on Sunday, Pro 10 said: "At no time did we authorise Mr Mallon to sell any tickets on our behalf nor to the best of our knowledge did he sell any tickets. He merely acted as a collection point for individuals transacting directly with ourselves."
Pro 10 said the tickets had already been paid for legitimately and Mr Mallon was not being paid by Pro 10.