While the PricewaterhouseCooopers report on Aer Rianta last week said its charges were among the lowest in Europe, it also contained several criticisms of the airports operator.

Firstly, the authors said Aer Rianta's charges do not always comply with the twin principles of "discrimination and cost relatedness". For example, Shannon, Dublin and Cork airports have different costs and volumes of traffic, but the basic charges are still the same, the report pointed out.

It also stated that Aer Rianta's discount scheme - where certain scheduled services are given discounts - was not available to charter services. It said it was hard to see how this "discrimination" was valid.

It also said it was difficult "to justify the discount given to British passengers, since they use virtually identical facilities to other international passengers".

While these remarks will not find favour with Aer Rianta, the overall message in the report was that its charges have to rise.

Of course this has been firmly rejected by Ryanair who said the report was not credible because it only used Aer Rianta's figures.

Aer Rianta has now commissioned another report on how much the charges should rise.

Before the summer they will submit this to the Minister for Public Enterprise, Mrs O'Rourke, seeking approval for the new charging structure.

She is likely to come under strong pressure from Ryanair not to give approval. Mrs O'Rourke already has a proposal on her desk from the airline to build its own terminal at Dublin Airport.

She has held more than one meeting with chief executive, Michael O'Leary, about this and other issues.

With the voluble Mr O'Leary on one side and Aer Rianta on the other, Mrs O'Rourke will have her work cut out to remain friends with everyone.