Fine Gael and the Labour Party tonight joined in Government tributes to Mr Peter Mandelson following his resignation as Northern Ireland Secretary of State.
The Fine Gael spokesman on Northern Ireland, Mr Brian Hayes, said he was disappointed at Mr Mandelson's decision to go.
"It can be argued that Peter Mandelson was a colourful and slightly controversial Secretary of State for Northern Ireland. He did, however, make an important contribution to the peace process, and this should not be overlooked, Mr Hayes said.
He also called on the British Prime Minister Mr Tony Blair to appoint as Mr Mandelson's successor, "an experienced person who has an in-depth knowledge of Northern Ireland affairs".
"Internal political considerations, in either London or Dublin, cannot be allowed to stand in the way of the full implementation of the Good Friday agreement.
"Any form of political instability at this time could damage the prospect of a final agreement taking place," he said.
Labour Party leader Mr Ruairi Quinn called Mr Mandelson's departure "a significant blow to the prospects for political progress in Northern Ireland, coming as it does at a time when talks between the two governments are poised at such a delicate point."
"I believe the Irish people owe Peter Mandelson a considerable debt of gratitude for the Trojan work he put in during his period in office - often in the face of hostile media and political comment," he added.