Taoiseach Micheal Martin has said it is important not to be "overly judgmental" of the attendance of senior Sinn Fein figures at the funeral of former senior IRA leader Bobby Storey.
Martin said Northern Ireland's institutions should not be damaged by the fallout from the scenes at the funeral earlier this month which was attended by Mary Lou McDonald, Michelle O'Neill, Gerry Adams and other senior Sinn Fein figures.
A PSNI investigation is under way into suspected breaches of Covid-19 public health guidelines after hundreds turned out for the funeral in West Belfast.
The Fianna Fail leader has been a strident critic of Sinn Fein's links to the IRA for the last decade, but adopted a noticeable shift in tone towards the party in an interview with BBC Northern Ireland's Sunday Politics programme which is being broadcast today.
Martin said he had lost good friends whose funerals he had not been able to attend in recent months and he understood "the anger and frustration of people" over the large turnout at the funeral in West Belfast.
However, he added: "As co-guarantor of the [Good Friday] Agreement, my overall perspective on this is to try and ensure that this doesn't damage, or undermine, the institutions within the North.
"We've had a long period without the Northern Ireland Executive and without the Northern Ireland Assembly. I think it's critical that now we have them back, that they're in a position to work in a cooperative and progressive way but also with momentum because of a lot of stuff that's signed up to by all parties.
"The one point I would make is we have to be careful not to be overly judgemental of people's behaviour. We all have to strive to do the right thing in respect of the public health advice, that is extremely important.
"We have to do everything we can to maintain social cohesion and solidarity in the following of that advice.
"If breaches occur, people should put their hands up and say I understand the anger, I understand where you are coming from in having a problem with what I did and I think we all learn lessons then from that and then we have to move on from that."
Martin said that "political competition or rivalry within the republic" as well as Fianna Fail's relationship with the SDLP, will not interfere with his approach as Taoiseach to implementing the Good Friday Agreement and "doing the right thing by the future of the island and the future of the North".
The Fianna Fail leader said he accepted and agreed with Sinn Fein's analysis that Brexit had changed the dynamic.
"The challenge now is how do we live together in a post-Brexit scenario and how do we manage to cooperate practically together in that scenario."
However, Martin said a border poll would be "unnecessarily divisive" and said he wanted to "move beyond the slogans" and get a more substantial proposition and understanding of the implications of a border poll.
Martin said he was a "passionate believer" in the Good Friday Agreement, but that the North-South dimension "needs resuscitation, needs a bit of extra momentum".
The Taoiseach said even a "normal Brexit" would have repercussions for the island of Ireland and North-South relations.
The Cork South-Central TD also defended his decision not to appoint a senator from the unionist background, rejecting as "unfair" and "disproportionate" the criticism of the decision by former senator Ian Marshall.