The outworkings of Brexit continue to "bedevil" politics in Northern Ireland, the Taoiseach has told an audience in Derry.
Micheál Martin was addressing an event organised by the Hume Foundation at the Playhouse theatre in the city.
Reflecting on almost a quarter of a century since the Good Friday Agreement, Mr Martin said there had been reconciliation across the islands.
He added: "But we also see that the three sets of relationships accommodated in the Good Friday Agreement are strained, and they have been for some time now.
"The outworkings of Brexit, including the protocol, continue to bedevil politics in Northern Ireland and complicate both north/south and east/west relationships.
"The power-sharing Executive and North South Ministerial Council are, once again, not fully functioning, which is a source of deep concern.
"As it the fact that the legacy of the Troubles has still not been equitably dealt with. Leaving unmet the needs and legitimate expectations of victims and unresolved trauma in society."
The Taoiseach spoke with business leaders on both sides of the border as part of a day of engagements in Derry.
Mr Martin also visited the medical school at the city's Ulster University Magee campus.
Earlier, he said that he did not think twice about visiting Northern Ireland after his Cabinet colleague Simon Coveney had to leave an event last week due to a bomb alert.
Mr Martin condemned the UVF bomb alert in Belfast last Friday that disrupted a speech being given by the Minister for Foreign Affairs.
He said he had been heartened by the cross-community condemnation.
"Democracy must always triumph. Society must have the freedom to engage, discuss and reflect," he said.
He said security for visits was a matter for the PSNI and gardaí and he would take his advice from them.
He said his Government listens carefully to all communities in Northern Ireland.
Mr Martin said: "The threat of violence last Friday targeting an innocent man, disrupting a family funeral in Belfast and the foundation's cross-community event with Minister Coveney, underscores how much we still need John Hume's message and means of peace-building today.
"I welcome that last week's incident, and the attack on Doug Beattie's office this week, have been condemned by political leaders from all communities, making clear that no purpose is served and nobody is represented by violence or a threat of violence.
"My government listens carefully to the concerns of all communities in Northern Ireland.
"As Taoiseach, I have engaged actively and constructively with unionist, nationalist and other political leaders across the spectrum here.
"The Irish Government will never dismiss genuinely held concerns around the protocol, and we are working very actively with our EU partners to listen and engage on them, but any opposition must always be peaceful. That is simply fundamental.
"There are democratic and lawful means for all concerns to be raised and resolutions worked through. That is where our focus must remain."
Ahead of the event, a number of homeowners affected by the mica scandal in Ireland staged a protest outside the theatre.
Additional reporting PA
