A planned development of 63 houses and apartments -opposed by Transport Minister Shane Ross - has been refused permission.
The Dublin Rathdown TD "strongly" objected to planned homes in Mount Merrion partly on the grounds that trees on the site needed to be protected.
The development would put "further unnecessary pressure on local schools and families", according to his submission.
He added that part of the site is designated "to protect and preserve trees and woodlands".
Dun Laoghaire-Rathdown County Council has now rejected the proposals by Balark Investments, a company asso- ciated with developer Greg Kavanagh, on the grounds that more than 150 trees would have to be felled and that the plans do not provide quality "usable public open space areas".
The council said the properties "would adversely affect the sylvan character of the subject site, would adversely affect the residential and visual amenity of future occupants of the proposed development and would be contrary to the proper planning and sustainable development of the area".
Balark has indicated that it will appeal the decision to An Bord Pleanala.
The Herald has also learned that Mr Ross met with council chief executive Philomena Poole yesterday to discuss "planning matters".
A council spokesperson said the meeting was requested by Independent Alliance minister and councillor Deirdre Donnelly.
"A meeting which was attended also by the Director of Planning took place this morning and an overview of the Dun Laoghaire-Rathdown County Council Development Plan was provided," the spokesperson said.
Mr Ross's spokesperson said he was not in a position to comment on the Mount Merrion planning decision.
The minister expressed his satisfaction last month after another planning application in his constituency was turned down.
The proposal for the Union Cafe site in Mount Merrion included a four to five-storey development with a cafe, restaurant and 46 residential units.
In his submission on the site, Mr Ross warned that it would be "negligent" to bring extra traffic into a "very quiet and peaceful suburb".
Fine Gael TD Josepha Madi- gan and the Green Party's Catherine Martin also objected to the development.