Ireland is too small for people north and south of the border to live in isolation of each other, Sinn Fein has claimed.
The nation's only all-island party said a new cross-border parliamentary group will help break down social and economic barriers.
President Gerry Adams welcomed the first meeting of the North-South Inter-Parliamentary Association, which was formed out of commitments made in the Good Friday Agreement.
"This is a very positive development," said Mr Adams.
"It reflects the increasing acknowledgement that Ireland is too small for our people to live in isolation from each other and that working together is better for everyone."
The group met within the houses of the Irish parliament for the first time. The group is made up of 50 members - 25 politicians from Northern Ireland, including unionists and nationalists, and a group of 25 cross-party TDs and senators from the Republic of Ireland.
The next meeting, in spring 2013, will be held at Stormont - home of the Northern Ireland Assembly. All meetings are to be co-chaired by the Dail's Ceann Comhairle Sean Barrett and Stormont speaker William Hay.
Mr Adams said while his republican party and unionists could not agree an end to the north-south divide, the association gives the opportunity to improve relations.
"It makes sense to develop the widest possible co-operation and co-ordination of public services and economic development by removing the social, economic and bureaucratic barriers to enhancing the quality of life of citizens on this island," he added.
"The Inter-Parliamentary Association provides another forum through which good relations and trust can be built. Greater harmonisation of our natural, human and economic resources can be agreed to our mutual benefit."