Fresh complications are clouding the planned use of a new €320m runway project at Dublin Airport after the Government dramatically backtracked on proposals to put the Irish Aviation Authority (IAA) in charge of enforcing an EU aircraft noise regulation.

Transport Minister Shane Ross has confirmed that fresh legal advice from the Attorney General's office has meant that it "would not be consistent with the principles of good corporate governance of the IAA as a whole" to appoint the authority as the competent body to enforce the legislation, contained in regulation EU 598/14.

The decision has left the Department of Transport scrabbling for an alternative to the IAA. An Bord Pleanála and the Department of the Environment are among the possible candidates.

Clare Daly TD claimed the inability of the Government to appoint the IAA as the competent body a year after it said it intended to do so, was a "catastrophic failure".

The EU regulation was introduced to reduce the noise impact from aircraft arriving and departing at airports in the trading bloc.

Its implementation could have consequences for Dublin Airport, where passenger traffic is expected to hit about 30 million this year.

The DAA, which controls Dublin and Cork airports, has almost finished site preparation work for the new runway, and a tender for the actual runway construction is expected to be awarded next year. The runway is due to be operational in 2021. Local residents and groups have mounted High Court legal challenges against the runway plans.

Planning permission was granted for the 3.1km runway with two conditions attached by An Bord Pleanála that will hamper its operational effectiveness, and that of the airport.

The two conditions include one that would prohibit the new runway's use between 11pm and 7am - a period that includes the airport's extremely busy morning operations. The second condition would cap the number of total flights at the airport between 11pm and 7am at 65. The airport currently handles about 100 flights during that time.

The DAA has previously claimed that if the runway opened with the two conditions in place, Dublin Airport would immediately see its annual passenger numbers cut by three million. The DAA wants to have the two conditions attached to the runway project rescinded.

But the DAA can't commence those efforts until a competent body has been named to oversee the EU noise regulations and necessary legislation has been enacted. All that, including an actual review of noise at Dublin Airport under the EU regulation, could take a year.

Ryanair chief executive Michael O'Leary warned during the summer that a delay by the Transport Minister in appointing a competent body to oversee the noise legislation could also hold up the opening of the new runway.

Mr Ross told Ms Daly that the noise regulation function was intended to be assigned to the regulatory division in the IAA, "and was to be managed on a functionally independent basis from the commercial activities of the IAA in the provision of air navigation services".

He added: "On foot of the most recent legal advice of senior counsel engaged by the Office of the Attorney General, it is clear that this approach is no longer advisable.

"Case law at European level has now led to a more strict interpretation of what constitutes functional independence within an organisation.

"I have already instructed my department to re-engage with the Department of Housing, Planning and Local Government, and Communications, Climate Action and the Environment, as a matter of urgency to consider the possible options for assignment of this role to an existing State body."

Irish Independent