The aviation regulator is proposing to allow Aer Rianta to increase the charges it levies airlines for using Dublin, Shannon and Cork airports.

But the rises - which could result in increased costs for airline passengers - will be linked to the State airports operator achieving service levels which the regulator has concluded can be significantly improved.

In the case of Dublin airport, the regulator, Mr Bill Prasifka, has concluded that it is 30 per cent less efficient than a peer group of airports of a similar size. He has also revised downwards Aer Rianta's figures for the cost of infrastructural improvements at Dublin and Shannon airport.

A draft proposal on maximum airport charges released yesterday by the Commission for Aviation Regulation provides for an increase in charges at Cork Airport by a maximum of 94 per cent to £7.15 (#9.08) per workload unit, while Aer Rianta could increase charges by 37 per cent at Shannon to a maximum of £6.05 and by 9 per cent at Dublin Airport to £4.96 per workload unit.

The workload unit is an international standard and equals the movement of one passenger or 0.1 tonnes of cargo.

The charges would be set for five years, but would be adjusted for inflation on an ongoing basis in that time period.

The proposed charges are the maximum that the airport operator can charge and it is free to negotiate charges under these levels with individual airlines.

The proposed increases in airport charges are tied to Aer Rianta's capital expenditure programme, but are based on the regulator's own estimate of the investment requirements at the three airports. The big rise in charges for Cork Airport reflects the need for large capital investment there.

However, the regulator's draft document said, with the exception of projects required for safety reasons, Aer Rianta had not justified its planned capital expenditure. It adjusted downwards the value of the proposed pier C at Dublin Airport by almost £21 million, while for Shannon Airport, the value of the most recent terminal building has been downwardly adjusted by more than £7 million.

At Dublin Airport, the regulator estimates the scope for improvements in operational efficiency to be 15 per cent over five years, while it said Aer Rianta could enhance efficiencies at Shannon by 25 per cent.

While the regulator found that Dublin Airport had a comparable level of efficiency to major European airports such as Heathrow and Frankfurt, against a peer group of airports of similar size, its efficiencies were 30 per cent poorer.

All interested parties have 30 days to make further submissions. Public meetings will be held on July 17th and 18th at the Great Southern Hotel at Dublin Airport. A definitive decision on airport charges will be published on August 24th.