The Housing Authority's planning application to build 46 apartments and garages in a beautiful valley at Luqa should be refused, Flimkien għal Ambjent Aħjar said.
It said in a statement that Mepa will again be discussing this application tomorrow, when it is also expected to take a decision.
Part of the site proposed to be developed was included in the 2006 rationalisation plans and is full of protected carobs and dry stone walls.
Facing the valley are rows of unsold new apartments.
FAA said the application was previously deferred owing to strong evidence submitted by Civil Aviation Authorities regarding the unsuitability of the site because it is situated within the Public Safety Zone of Runway 23 as defined by the Civil Aviation Directorate and only about 460 metres from the safety threshold.
The Public Safety Zone aims to control and limit the number of people on the ground in a high-risk area in the event of an aircraft accident. The basic policy regulating the restriction of development near civil airports is that there should be no increase in the number of people living, working or gathering in PSZs and that over time the number of people on the ground should be reduced and not increased.
In its reply to MEPA's request that MIA provides a list of conditions to be included to approve the development, MIA contended this would amount to automatic sanctioning of development in an area of known public risk, which would be "conducive to arbitrary and imprudent dismissal of the envisaged public risk at this site by MIA".
FAA said that while it may not be within the remit of the MEPA board to take decisions regarding social housing on behalf of the Housing Authority, there was no question that wise planning was MEPA's responsibility.
"In view of Malta's over 76,000 empty units and our increasing flooding problems, MEPA should prioritise the use of existing vacant housing units and actively discourage the building up of more of Malta's valleys.
"This is especially true of a government authority which should be setting an example of sustainable development," FAA said.