Finance Minister Sammy Wilson's decision to give greater weight to economic benefits in planning applications was “hopelessly flawed”, the High Court has heard.
Lawyers for a major retail company claim Assembly statements he made while running the Department of the Environment amounted to new policy being implemented without proper consultation.
Central Craigavon Limited, owner of the Rushmere shopping centre, wants the position adopted by Mr Wilson to be quashed.
The company believes it has made it easier for a rival development at Sprucefield, near Lisburn, to go through.
The case, which could have significant implications for large-scale planning applications in Northern Ireland, centres on two declarations by Mr Wilson last May and June.
He told the Assembly how economic factors should be given greater emphasis when planning bids are assessed.
Then, in a separate statement, he confirmed planners would only reject major applications on the grounds of prematurity if approval would prejudice or undermine a development plan.
Mr Wilson has since become Finance Minister, but the DoE is said to have maintained the position.
Central Craigavon Ltd is seeking a judicial review of this stance by claiming it represents a change of policy which should have been agreed by the Stormont Executive and gone out to other interested parties for consultation.
The retail firm argues that the shift has lowered the hurdles the Sprucefield scheme has to clear.
In court yesterday John Larkin QC contended that the statements were issued for no other reason than to set the framework for future development.
Mr Larkin set out how Mr Wilson may have “erred” either constitutionally or by unwittingly making policy. The barrister told Mr Justice Treacy: “Whichever way it's looked at, these statements are hopelessly flawed and we respectfully invite your Lordship to quash them.”
However, counsel for the department denied a new policy was in place, and said the position did not merit being brought to the Executive.
Paul Maguire QC pointed out that many issues come before the Executive without any legal obligation to do so, said Mr Wilson wrote to the First and Deputy First Ministers and received approval five days before he made the Assembly statement last May.
Judgment in the case is expected to be delivered at a later date.