Failure to approve a €300 million development plan for Dublin's O'Devaney Gardens would cause a five year delay in providing a total of 1,500 homes according to a city council report.
Assistant chief executive Brendan Kenny is asking councillors to pass "this vital project" for 824 homes on the north city site with a 50% private, 30% social and 20% affordable mix.
If councillors refuse to pass the plan then the O'Devaney plan and a similar scheme in Coolock would have to be abandoned involving a total of around 1,500 homes, he warned.
Although the O'Devaney plan was passed by the previous council in January 2017 there have been increasing demands for the deal to be renegotiated or even scrapped altogether in favour or more public housing and cheaper affordable units.
Councillors are due to vote on the plan next Monday and the Dublin Agreement group which consists of Green Party, Fianna Fáil, Labour and Social Democrats, and which holds a majority on the council, are meeting on Friday night.
Fine Gael are in favour of the plan, the Social Democrats are opposed while Fianna Fáil and the Green Party have yet to decide on a final position.
Meanwhile, Sinn Féin wants a renegotiation and most Independents and People Before Profit will vote against.
Brendan Kenny has warned that if the plan is not approved then the procurement process will have to be abandoned and "we realistically would estimate that it could be another five years before we would reach the stage the project is currently at".
He said a similar process at the Oscar Traynor site in Coolock would also have to be abandoned leading to a loss in the region of 1,500 new homes.
Both sites are being developed under a scheme known as the Land Initiative in which developers can bid to build an agreed scheme and housing mix on council owned land.
The winner of the procurement process for O'Devaney was Bartra Limited which has been involved in a number of co-living schemes in the capital.
Mr Kenny in his report emphasises that the O'Devaney scheme will not have any student, shared or studio accommodation.
He pointed out that the prices for social and affordable housing would be fixed over the time of the development equivalent to a cash saving of €19 million.
Prices for affordable units would range from €240,000 to €250,000 for a one bed apartment and up to €300,000 to €350,000 for a three bed house.
The deal also includes a discount from the developer for social and affordable units of around €32 million, the developer will also be providing infrastructure worth €10 million and making a cash payment of €7 million.