The Planning Appeals Commission was wrong in law to grant permission for a car park near Belfast International Airport, the High Court has heard.
Lawyers for the Department of the Environment (DoE) said the green light was given despite a finding that there was no demonstrable need for the facility.
In an unusual move, the DoE is seeking to judicially review the Commission's decision to authorise the Easi-park site.
Counsel for the Department claimed yesterday that there had been a failure to carry out a balancing exercise between two separate planning policy statements.
Although the car park was found to comply with policy PPS21, dealing with impact on the countryside, the Commission held that it breached another, PPS3.
Barrister Charles Banner said this was due to a lack of any demonstrable need for the car park and that granting of planning permission in those circumstances amounted to an error of law.
The hearing is scheduled to continue today.