The threshold had originally been set at 10,000, but was doubled after political pressure.
Homeowners in four Kildare towns can continue operating Airbnb-style rentals without falling under new national restrictions.
Maynooth, Leixlip, Athy and Kildare town are all below a new 20,000 population cut-off agreed by Government.
That means the tougher rules - which would have required planning permission and registration for short-term lets - will not apply in those towns.
The threshold had originally been set at 10,000, but was doubled after political pressure.
Critics say the change weakens efforts to push more homes back into the long-term rental market.
The Green Party says changing regulations on short term lets is pointless unless the rules are actually enforced.
It's expressing disappointment at the decision to introduce restrictions for areas with a population of 20 thousand people and not 10 thousand as originally proposed.
Eight Special Needs Assistants To Be Axed Across Two Kildare Schools Despite Budget Boost
Obituary Notices
Agriculture Minister Martin Heydon To Convene Urgent Talks Amid Bord Bia Dispute
More Than 1,300 Crimes Committed By People On Bail In Kildare/Carlow Last Year
Hundreds Of People In Ireland Died By Suspected Suicide After Contact With Health Services
New Framework To Reform Irish Defence Forces Heads To Cabinet
Overbidding At Auctions Putting Homebuyers Under Intense Pressure
Woman Allegedly Attacked With Weapon After Being Ordered To Delete Photo Of Attempted Break-In
