Louth TD Fergus O’Dowd signalled, during a long party meeting on the national planning framework, that he may lose his seat if there is a decision not to designate Drogheda as a city in the future.
Economic-led reasoning for development over social needs under the plan also outraged some TDs and senators at the meeting.
The private meeting in Leinster House heard that, without proper planning, Dublin would sprawl even further.
A four-page presentation given to members said other cities will grow too slowly, rural towns could face decline, and “transport chaos” would derail Ireland’s targets on climate change.
The new plan is not a blueprint for every county, but a chance to set a path for the country over the next five to 20 years, the meeting heard.
In the years ahead, the plan is to keep demographic regional shares at the current levels by 2040, with 50% in Dublin and the East region, 33% in the South Region, and 17% in the North and West.
This prediction angered some Fine Gael members.
Mr O’Dowd was one of the most prominent to speak out. He said that, by 2030, Drogheda would have more than 50,000 people and must be categorised as a city.
According to Fine Gael colleagues, he said he had been in politics since 1975 and would not stand for this, especially after getting grief recently on doorsteps about support for the Louth town.
A source said: “He didn’t threaten to leave, but he said he wouldn’t be back [re-elected] over it.”
He also took issue with a suggestion from Sligo TD Tony McLoughlin that his home town should be afforded a city status, with the Louth TD saying Drogheda would be twice its size.
Limerick senator Kieran O’Donnell questioned why plans for the N28 in Cork were not mentioned, while Junior Finance Minister Patrick O’Donovan had concerns for development around his home town of Newcastle West, Co Limerick.
Cork senator Tim Lombard and Longford-Westmeath TD Peter Burke expressed concern about the lack of rural housing plans and supports.
Some party sources claimed Mr Murphy was “ripped apart” at the three-hour meeting over the framework.
The 10-year capital plan is expected to outline, in the coming weeks, projects worth tens of billions of euro for parts of the country.