A public inquiry into proposals for a flagship John Lewis store will be delayed again after opponents won the right to mount a new legal challenge.
Traders have fought against the proposed 500,000 sq ft retail expansion at Sprucefield near Lisburn.
On Friday objectors were granted High Court leave to seek a judicial review over alleged irregularities in advertising environmental information.
A long-awaited public inquiry into the scheme is to open on Monday.
The owners of the retail centre have been trying to get approval for the store since 2004.
But traders from rival retail hubs Bow Street Mall and Central Craigavon Ltd launched proceedings against how environmental issues were dealt with.
They claim it should have been up to the Department of Environment, rather than the applicant, to place newspaper advertisements about the scheme.
The barrister for Bow Street Mall told the High Court that his clients only learned of the advert a week after it first appeared.
He said it gave members of the public four weeks to respond, arguing this meant views could be submitted as the inquiry is due to close.
The barrister claimed there had been an attempt to "fast-track" what has become the third application for the John Lewis store at Sprucefield.
Mr Justice Treacy granted leave to apply for a judicial review over how the environmental advertisement was placed.
Lawyers are now expected to seek to have the inquiry adjourned as soon as it begins on Monday until after the High Court proceedings are resolved later this year.
A spokesman for some of the objectors said: "It is very clear that there is a question mark around whether or not the Department should have advertised the new environmental information, which is absolutely crucial to this inquiry.
"Therefore, given that the full judicial review will be heard in September, it would appear to make the running of the inquiry next week very doubtful."
The legal challenge is the latest twist in the protracted bid to realise an expansion to Sprucefield Park first announced in 2004.
Up to 2,000 jobs were to be created, including around 700 at the first John Lewis store in Ireland.
Planning permission was granted at first, only to be overturned following a legal challenge by other traders.
They object to the building of a large-scale retail project which they said could damage town-centre shopping.