Plans to build 611 apartments on former RTE land are akin to "Ballymun Towers South Dublin" and could become "modern-day slums", businessman Dermot Desmond has claimed.
In a letter to local politicians, the billionaire threatened to use his "resources" to fight fast-track planning laws being applied to the development "all the way to the European Courts".
Mr Desmond, who owns a property on Ailesbury Road close to the Dublin 4 site, says the planning system "has been compromised" by Strategic Housing Development (SHD) legalisation.
The law allows planning applications for developments of more than 100 homes on land zoned for residential use to bypass local authority scrutiny and be directly assessed by An Bord Pleanala.
Cairn Homes has submitted plans under the SHD rules to build 611 apartments and three town houses on land it brought from RTE in Donnybrook, Dublin 4, in 2017 for €107.5m.
The project is close to Dublin's so-called "embassy belt" where ambassadors and other wealthy individuals live.
In a letter sent to Housing Minister Eoghan Murphy and other local representatives, Mr Desmond said it will be "higher than the density of Ballymun Towers North Dublin, built in the 1960s to accommodate a housing crisis and subsequently demolished and replaced by low-rise homes".
The financier argues that with more people working from home and high-tech electric transport in the future "there will be no need for these skyscrapers, which will become modern-day slums".
Writing specifically about the RTE development, Mr Desmond said the sale of the land to Cairn Homes "makes no sense" since Dublin City Council is now signed up to pay €30m for social housing in the development.
His wife Pat and two other Ailesbury Road residents have already launched a legal challenge to fast-track planning laws in the High Court.
Mr Desmond claimed the proposed height of the RTE development, ranging in height from four to 10 storeys, was "totally unsuitable to the area".
Cairn Homes said it was "Ireland's largest home builder delivering thousands of well-designed and constructed new homes to first-time buyers, other individual purchasers, pension investment institutions and the Part V social housing programme".
The company added: "The planning process we adhere to is managed by local authorities and An Bord Pleanala in a rigorously independent manner consistent with the Government's National Development Plan."
It pointed out that before the start of the process representatives actively engaged with neighbours and communities.
"As Cairn has now formally lodged its planning application for Montrose, Dublin 4, it is precluded for making any further comments," it added.