Cross-border economic cooperation between Derry and Donegal is already underway, TDs in the Dáil heard during a debate on the fiscal implications of a united Ireland.

Finance Minister Simon Harris said the economic dividend of reunification would be most visible in the north-west. He noted that counties like Donegal, Derry and Tyrone have been at the edge of two jurisdictions rather than the centre of a single economic region.

Donegal Sinn Féin TD Pádraig MacLochlainn outlined ongoing collaboration. He said First Minister Michelle O'Neill recently visited Letterkenny Chamber of Commerce, meeting with Donegal County Council, Atlantic Technological University, Donegal ETB and local businesses.

This group is working with Derry Chamber of Commerce to market the north west city region. Councils in Donegal, Derry and Strabane, and universities including University of Ulster and Northwest College are involved.

Mr MacLochlainn said 40 per cent of passengers using City of Derry Airport come from County Donegal, illustrating the integrated nature of the region.

He contrasted this with the historical impact of partition, stating that 100 years ago Belfast was larger than Dublin and accounted for 80 per cent of the island's industrial output, but has since fallen behind.

Dublin Fingal West TD Louise O'Reilly said partition had constrained Belfast's growth and that Derry must be allowed to reach its potential unhindered by the border.

Kildare North TD Réada Cronin raised the democratic deficit, arguing that British Chancellors who make fiscal decisions for Northern Ireland answer to voters in Britain rather than local communities, and that a united Ireland would give the region a government solely focused on Ireland.