Taoiseach Micheál Martin has warned of "very serious harm" if people keep trying to use Brexit to create points of dispute or by presenting every issue "as a zero-sum, win-lose fight".
He also said the Northern Ireland protocol to the Withdrawal Agreement “is a fair conclusion to attempts to limit the potential destructiveness of Brexit on this island”, despite unionist demands for it to be scrapped.
Mr Martin said the protocol “is complex, but it is nowhere near as complex as it is presented.
“It is not as complex as the thousands of Brexit issues remaining in relation to trade and other contacts between Great Britain and the European Union. Rules and connections developed over half a century don’t come apart easily.”
“With good faith and co-operation, disruption can be limited and we can resolve outstanding issues. We’ve seen important progress in recent days.”
Mr Martin was speaking at the annual Fianna Fáil 1916 Rising commemoration at Arbour Hill in Dublin.
“It is important to say that very serious harm can come if we keep seeing people trying to use Brexit as an issue to create points of dispute. Or by presenting every single issue as a zero-sum, win-lose fight.
“When this approach is followed in relation to UK-EU relations the damage it causes is primarily economic. When it involves misrepresenting the arrangements for Northern Ireland the damage can go much further.
“And this also gets in the way of understanding two basic points about the post-Brexit arrangement for Northern Ireland.
“First, it leaves constitutional issues solely in the hands of the people. It has absolutely no implications for national identity or any other substantive issue. Second, and just as importantly, Northern Ireland now has the unique position of benefiting from free access to the markets of both the UK and the EU.”
He said “we’ve seen in recent weeks what can happen when sectarian tensions are left to grow and are then encouraged by political events.
‘Good faith and co-operation’
“The terrible scenes on the streets of Belfast have deep roots which we must challenge – and it falls to all of us to play a constructive and moderating (role). With good faith and co-operation, disruption can be limited and we can resolve outstanding issues.
“We’ve seen important progress in recent days. We have worked with the EU and the UK to focus on how to tone down the disputes and show how the arrangements for Northern Ireland can work. With openness and good faith, we can deal with this difficult period.
Describing the Belfast Agreement, signed 23 years ago, as both a “practical and a visionary document”, he said “it delivered peace and demanded reconciliation.
“It understood that the communities on this island knew too little of each other and that we needed to build bridges between us, bridges of understanding and shared purpose.”
Referring to calls for a border poll on a united Ireland, he said the mechanics of the agreement were specifically designed “so that we would not have to see every single interaction through the lens of one, big constitutional decision”.
Since the signing of the agreement “we have lost too much time. Too little has been done to build essential links, to create new opportunities and to show people how much we can achieve through co-operation.”
He said the Government’s Shared Island initiative was only beginning but could have a huge impact.
Separately, former taoiseach Bertie Ahern said it was time for a meeting of the British Irish Intergovernmental Conference as there is currently no political engagement between the two governments.
Speaking on RTÉ’s The Week in Politics he said there seems to be a reluctance on the British side to engage with the Irish Government.
Mr Ahern, one of the negotiators of the Belfast Agreement, said there have been no meetings since British prime minister Boris Johnson took office and one should be arranged.