A permit application for the building of new residential blocks on Manoel Island was deferred by the Planning Authority on Thursday for clarification of whether the site lies within Valletta's heritage buffer zone.
The application, which had been slated for approval, is for the construction of 323 apartments across three large condominiums as well as two commercial spaces.
The Planning Board asked the PA's directorate to clarify UNESCO status concerns with Malta's cultural heritage watchdog.
In a statement on the eve of the hearing, Moviment Graffitti and Flimkien Għall-Ambjent Aħjar raised concerns that the development, having a total footprint of over 20,000 square metres, could impact the views from Valletta and endanger the capital city's UNESCO status.
Midi, the company that manages Manoel Island, applied for the full development permission after a masterplan for the area was approved in 2021.
The PA case officer recommended the project be approved, even though the proposed new buildings would take more of the island than had been approved in the masterplan.
The board's decision to defer its decision over heritage concerns comes a week after it revoked its own approval of a block of apartments in the buffer zone of Gozo's Ġgantija temples.
The board approved the 22-apartment block of flats with 20 basement garages in November despite UNESCO's request for a heritage impact assessment.
The board reconsidered its decision following calls by the Superintendence of Cultural Heritage and a coalition of Gozitan NGOs.