Three quarters of delegates backed a Central Council motion at Congress to introduce the change for the next three seasons.
Teams in Division Three and Four of the League will play in the new 16 team second tier, unless they reach their provincial final.
A Tipperary motion was carried to determine that Tier Two standings will be determined at the end of the League rather than at the start.
Wicklow Surgeon Honoured By Tallaght University Hospital
Extra Lifeguards Deployed With Extended Hours On Wicklow Beaches This Week
Bus Service Boost For Wicklow with Connections to Carlow & Kilkenny
Greystones Man Given Suspended Sentence Following Sustained Campaign Of Abuse
Appeal for Information As Rathdrum Man Reported Missing