An environmental group has complained to the Northern Ireland Ombudsman about a development at a Belfast golf club.
Houses were to be built on the grounds of Knock Golf Club, part of which is leased from the Ulster Hospital.
The club wanted to keep five acres of the 12-acre plot in return for giving up the lease 50 years early, freeing the remaining land for hospital use.
Dundonald Green Belt Association has alleged 59 failures were made in processing the planning application.
In a statement, it said the office of Ombudsman Tom Frawley should "be able to deliver the severest penalties for government departments found guilty of maladministration".
"These powers were promised three years ago. They haven't been delivered. Why not?" said a spokesperson.
The ombudsman can make recommendations but does not have the power to enforce them.
Stormont's Environment Committee is investigating fresh allegations about the planning application.
The planning application involved reducing the current golf course to nine holes and building 300 houses, including some social housing.
Separately, the club's new golf course would be constructed on a greenfield site at another location.
The planners - in coming to their decision to approve the application - considered that the early ending of the 100-year lease would be a "community benefit" because if the hospital carried out developments on the remaining land, it would be advantageous to the wider population.
An original application was turned down because it did not meet with planning guidelines.
This was subsequently amended and won approval, despite an objection from a senior planning official.
As far back as 2007, the development was supported by DUP MP Peter Robinson, who wrote to the then Environment Minister, Arlene Foster, asking if she could investigate the matter.