Sinn Féin today said it would welcome parties from the Republic contesting northern politics.
Fianna Fáil is considering organising in the North and it is widely seen as a direct challenge to Sinn Féin's claim to be the only all-island republican party.
But party president Gerry Adams said a move North should be matched by speaking rights for northern politicians in Leinster House.
"We welcome this development - in its own way it can help erode the partitionist mentality that pervades so much of Fianna Fáil's politics," Mr Adams said.
He said the SDLP would be hit hardest by competition from Fianna Fáil. "The SDLP is now a party without direction; unable to come to terms with its own electoral setbacks; trying to carve out a space in the Assembly as a party in government and in opposition at the same time; and undecided as to whether it joins the UUP or Fianna Fáil," Mr Adams said.
He was speaking at the party's annual Edentubber commemoration in north Co Louth
Fianna Fáil has signalled several times in the last six months it is planning a cross border move. Last month a party think-tank, the Northern Ireland Strategy Committee chaired by Foreign Affairs Minister Dermot Ahern, held its first meeting to discuss the idea.
It is taking soundings from party members and is also likely to seek opinions from the North. While the party officially appears keen to move north, it has insisted it does not plan to contest Westminster seats.
Meanwhile, Republican Sinn Féin again rejected a request for talks from Mr Adams. Party president Ruairi O'Brádaigh told his ard fheis in Dublin that his party's core values "that no reconciliation is possible".
PA