The Equality Authority is investigating a "substantial number" of complaints from passengers who say Ryanair charged them up to €25 each for the use of a wheelchair.
The airline is the only one in Ireland which passes on these charges to wheelchair-users and disabled passengers claim they have been discriminated against.
The authority's chief executive, Mr Niall Crowley, said the complaints "raised serious issues" under the Equal Status Act, which outlaws discrimination.
Under this legislation, a service provider may be forced to pay compensation or change their policies if complaints are upheld by the Office of the Director of Equality Investigations.
In a separate move, Ryanair is facing a class action from more than 50 British passengers who say they were discriminated against due to the airline's wheelchair policy. The British Disability Rights Commission is preparing the cases against the airline and the British Airports Authority.
A spokeswoman for Ryanair said it provided full assistance to wheelchair passengers without charging, but insisted it was not up to the airline to provide a wider service for free.
"Ryanair flies from the UK to 84 destinations and at 78 of these airports wheelchair service is provided free of charge.
"There are four airports in the UK that charge for this service. Two airports in Ireland - Dublin and Cork - also have the charge. It is not up to us to provide this service," the spokeswoman said.
The Irish airports authority, Aer Rianta, said wheelchair services were provided by a private company, Greencaps, and that all airlines, except Ryanair, were prepared to absorb these costs.
A spokeswoman said it was matter for the airline to pay for the wheelchair service while it was the airport's responsibility to ensure the building was wheelchair-friendly.
The chairwoman of the Disability Authority, Ms Angela Kerins, said she welcomed the Equality Authority's investigation into the matter and said it would be "good business practice" if Ryanair ceased charging wheelchair users. "There are 30 million disabled tourists in Europe. What's good for the disabled is good for tourism. Maybe the airline is not looking at the advantages of having these tourists in its flights," she said.
Under the Equal Status Act, the provider of a service must do "all that is reasonable" to accommodate the needs of a disabled person by providing special facilities.
The service provider is exempt from doing so, however, if provision of these facilities would "give rise to a cost other than a nominal cost".
The controversy comes just a week after Ryanair announced record profits of €240 million, a rise of 60 per cent.
The firm's chief executive, Mr Michael O'Leary, said he intended to keep the pressure on competitors by aggressive fare-cutting.
He added that Ryanair expected to become Europe's biggest internationally scheduled carrier, beating Lufthansa and British Airways, within three years.
"We're going to destroy the airline business as we know it," he told Reuters last week.
