Report 'has implications for talks'
Unionist politicians called on Dublin to acknowledge the role the Irish government played during the Troubles after the release of the Smithwick report.
"I believe that the finding of collusion on the part of the Garda with members of the IRA is significant and has major implications for the way in which we deal with the past under the current talks process being overseen by Dr Richard Haass," he said.
The DUP's Arlene Foster said the findings are damning.
"All too often we have seen the Irish Government call for investigations into events in Northern Ireland but take grave offence at suggestions of wrongdoing from within their state," she said.
"This must act however as a catalyst for further movement towards acknowledgement by the Irish Government of the role played by Dublin in the formation of the IRA and how republican terrorists were able to operate across the border with relative ease."
Northern Ireland's Justice Minister David Ford said a rogue officer acting outside the law should not result in the loss of trust between the PSNI and gardai.
"Since taking up this office I have worked to build the levels of co-operation between the two services and Alan Shatter and I, as the two ministers, will continue to do this," he said.
Theresa Villiers, Secretary of State for Northern Ireland, said she will raise the collusion scandal with the Irish Government.
"An important point to remember is that levels of co-operation between An Garda Siochana and the PSNI are now at unprecedented levels and are playing a crucial part in combating terrorist attacks in Northern Ireland," she said.
The SDLP's Dolores Kelly commended Judge Peter Smithwick for his independent and fearless approach.
"Judge Smithwick, through a trying process and painstaking work has gotten to the bottom of this tragedy," she said.
"The fact that Judge Smithwick identified 'misguided loyalty' that resulted in certain matters being covered up is a matter that the Irish Government must now reflect on and address."
Ulster Unionist MLA Tom Elliott claimed successive Irish governments have not done enough to stop the IRA, while TUV leader Jim Allister called the findings a devastating exposure of the Garda complicity in IRA murder.
"The report has confirmed what we already knew..." he said.
"Throughout the Troubles the Republic was effectively a safe haven for Republican criminals and it comes as no surprise that the Garda colluded in the murders of Chief Supt Harry Breen and Supt Bob Buchanan.
"It is time for Dublin to come clean on their role in arming the IRA and facilitating their campaign of terror, not, as some unionists have suggested, to 'draw a line' under the issue."
Meanwhile Sinn Fein president Gerry Adams said the collusion uncovered in the tribunal was different from what went on in Northern Ireland.
"During 30 years of war the British state was responsible for structured, institutionalised and co-ordinated state-run collusion and death squads which led to the deaths of hundreds of citizens, including those killed in the Dublin and Monaghan and Dundalk bomb attacks," he added.
"The British Government refuses to hand over vital information on these.
"Sinn Fein believes that there needs to be an effective truth process for dealing with all legacy issues," he added.
Amnesty International Ireland also called for the establishment of a single, comprehensive mechanism into 30 years of human rights abuse in the north.
"There are outstanding allegations concerning wrongdoing by agents of the Irish state in other cases," said Patrick Corrigan, of Amnesty Northern Ireland.
"We now need a new mechanism to investigate the past in Northern Ireland and full co-operation by the Irish authorities with this process."