Independent airline Ryanair has received nearly £23 million in rebates from Aer Rianta in the past four years, it has emerged. Ryanair has been a persistent critic of the airports' authority for the charges it levies on the users of its airports at Dublin, Shannon and Cork.

A Clare Fianna Fail TD, Mr Tony Killeen, yesterday released details of a written Dail reply he received last week from the Minister for Public Enterprise, Ms O`Rourke. She revealed that Aer Rianta had given rebates of nearly £57 million to its airline customers over the past four years. Ryanair was the principal beneficiary, though Aer Lingus was not far behind with £21 million.

In 1997 alone, Mr Killeen was told, airlines serving Dublin got discounts worth £20 million compared to £1.6 million for Shannon. In the past four years, Ms O`Rourke said, 86 per cent of the rebates went to airlines serving Dublin, compared with 7 per cent for Shannon and 6 per cent for Cork. Ryanair does not currently serve Shannon.

A spokesman for Aer Rianta said yesterday it had been traditionally reluctant to give details of the rebate scheme for commercial reasons. But once the Minister had been asked a Dail question, it had no choice but to release the figures, the spokesman added.

"It suits us in some ways to have the figures out in the open," the spokesman said. "It annoyed the hell out of us to have Michael O`Leary [Ryanair's chief executive] going on about our high charges when Ryanair was getting rebates on that scale."

The rebate scheme was designed by Aer Rianta to develop new traffic through its airports. The spokesman said that the rebates took the shape of Aer Rianta foregoing landing fees and passenger load fees if the airlines reached agreed growth levels.

Mr Killeen said yesterday he had sought an urgent meeting with Ms O`Rourke and Aer Rianta's chief executive, Mr John Burke, about the operation of the rebate scheme, which he said was heavily tilted towards Dublin. Mr Killeen said he would be seeking an explanation as to why Delta Airlines got three times more in rebates for landings in Dublin than it did in Shannon.

The Aer Rianta annual report for 1997 showed that Dublin had a 10,000 increase in aircraft movements, turnover grew from £231 million to £246 million and profits grew from £37 million to nearly £43 million. By contrast, Shannon showed a decline in aircraft movements.