The aviation regulator, Mr Bill Prasifka, will spend almost half his budget this year defending a legal action taken by Aer Rianta. The State airport company has secured a judicial review against Mr Prasifka's determination on airport landing fees.

The determination criticised Aer Rianta's €1.27 billion capital expenditure programme and said only a quarter of it was necessary. It reflected unhappiness throughout the airline industry with the airport company's plans.

It is understood the Commission for Aviation Regulation has projected expenditure of about €1.75 million for its defence of the action. This is in addition to ordinary expenditure of about €2 million.

If he loses the judicial review, it is thought Mr Prasifka will have to recover the legal expenses from the industry in the form of increased levies.

The regulator is expected to publish proposals today on a levy to fund the office.

Such fees will be charged to Aer Rianta, the airlines and companies that use the airports, and to the Irish Aviation Authority which operates air traffic control services.

An Aer Rianta spokesman said no definitive figure had been put on its legal costs for the judicial review. He added: "On the basis that the company expects a successful outcome, it looks forward to having the costs paid for it."

Referring to the levy, the regulator's director of corporate affairs, Mr Cathal Guiomard, said: "We have to cover our costs in some fashion and we will be putting our proposals to the industry."

He added: "The amount of the levy is ... based on actual past expenses incurred in carrying out the commission's statutory responsibilities and budget estimates for this year.

"The commission is now inviting discussion on the manner in which these sums may be recovered through the levy from the different parts of the aviation industry."

It is thought that Mr Prasifka's office had outgoings last year of about €3.5 million. A significant portion of that expenditure was incurred employing consultants during his determination on fees.

Costs incurred in the establishment of the office were met by the Department of Public Enterprise, which had responsibility for the commission before its formal establishment on February 27th last year.

The determination on airport fees increased landing fees last year in anticipation of a decrease this year and in later years.