The Minister for Transport, Mr Brennan has said he "cannot accept" that a person would buy a taxi licence exclusively for his own use and not for the benefit of the public.
Mr Brennan was referring to reports that Ryanair chief executive Mr Micheal O'Leary has spent €6,000 on a taxi plate for his chauffeur-driven Mercedes, so that he can use bus lanes to beat the traffic.
Commenting through his spokesman yesterday, Mr Brennan said it was his personal view that, if a person is granted a licence for a public-service vehicle, it is assumed it is on the basis that the vehicle will be available to the public.
Mr Brennan said he would, "find it hard to accept that a person would use a public-service licence in this way, as a dedicated car for himself".
Last night Mr Brennan requested that the new Interim National Taxi Regulator, Mr Jimmy Farrelly, investigate abuses of the licence-plate system and examine the adequacy of existing regulations governing entry into the taxi sector as part of his industry review.
He has also asked officials in his Department to examine the regulations and legislation to establish the exact position in law of "the issuing of taxi licences to business concerns or individuals for their own private use and not for the provision of a service for the benefit of the general public".
It has been reported that Mr O'Leary purchased the plate from Westmeath County Council and registered it to a company of which he is secretary.
A spokeswoman for Ryanair confirmed the purchase last night. "To the best of my knowledge it is true and what is reported in the papers is correct," she said. Mr O'Leary was not available for comment.
Fianna Fáil TD and member of the Dáil Transport Committee Mr Martin Brady said that, while there was nothing illegal about private citizens purchasing a taxi licence and not running a taxi business the Interim Taxi Regulator must put in place a system whereby taxi-plate holders must produce evidence stating they are running a taxi business.
"The use of a taxi plate by private citizens is certainly not in the spirit of what taxi-plate allocation is about in Dublin."
The Labour Party Spokesperson on Transport, Ms Róisín Shortall, said yesterday that the problem of individuals acquiring taxi plates for private use extends beyond Mr O'Leary. "There have also been reports of other wealthy individuals and firms also acquiring licences."
This "abuse" of the taxi regulations is unfair to other taxi drivers and to the commuting public, she said. "The purpose of the bus lanes in the first place was to speed up public transport and encourage people to leave their private cars behind. . . Chauffeur-driven cars of the super wealthy are not available to the public and should not, therefore, be entitled to use bus lanes."
Labour Councillor, Mr Kevin Humphreys tabled a motion calling for a review of the issuing of taxi plates at a meeting of Dublin City Council last night.