The vacuum in Stormont powersharing is causing real damage, Fianna Fail leader Micheal Martin warned.
Devolved Government has been suspended for more than a year and Mr Martin said there was no local voice to address mounting problems in hospitals and schools in Northern Ireland.
He claimed Sinn Fein and the DUP bore primary responsibility for dysfunction and inaction which put party ahead of public interest but added: “The simple fact is that the governments also bear serious responsibility.
“They may talk to each other a lot, but they seem unwilling to show urgency or serious leadership.
“A vacuum has been created which is grave and is causing real damage.”
The British and Irish Governments have been leading efforts to resurrect the devolved institutions, with nationalism opposed to direct rule from Westminster.
Recent reports have suggested an alliance between Fianna Fail and the SDLP, which has struggled at the polls in recent years.
Mr Martin made no reference to that during a speech in Dublin but warned no local voice was involved as critical services were planned.
He added: “No voice to address endemic poverty in marginalised communities.
“Most of all there is no place for Northern Ireland at the table when its future is being decided in Brexit negotiations.”
The British Government recently set a budget for public services in consultation with the Northern Ireland Civil Service.
Mr Martin addressed Fianna Fail’s 1916 Commemoration at Arbour Hill on Sunday.
Disagreements over a law protecting the Irish language have bedevilled efforts to restore powersharing.
Former Deputy First Minister Martin McGuinness resigned in protest at the DUP’s handling of the over-spending Renewable Heat Incentive (RHI) scheme, forcing the collapse of the institutions.
Endless series of political talks involving the main Stormont parties, the British and Irish Governments have failed to bring about a restoration.
Those subjected to historical child abuse in religious residential homes have also seen bids for official support delayed.