Sinn Féin chief negotiator Martin McGuinness has urged the Government to stop pandering to unionists.
Mr McGuinness said all too often at critical junctures in the peace process, the Government had allowed itself to be treated as junior partner and had failed to act with the same determination as the British government.
"Their approach has been clouded by a belief that unionists must be pandered to, even when this short-sighted approach has seen talks collapse in the last two years," he added.
Mr McGuinness renewed his appeal to the killers of Robert McCartney to "do the honourable thing", adding that those with information should do the same.
"There can be no place within Irish republicanism for those who perpetrated this terrible deed," he said. "Nor can there be any place within Irish republicanism for anyone who by his or her silence would attempt to cover it up."
He said those responsible should come forward primarily because the murder of Robert McCartney was a crime.
"But not to do so is not only cowardly but also equally despicable as they are allowing their own community to be vilified and demonised," he added.
Speaking yesterday at the party's Easter commemoration at the GPO, in Dublin, Mr McGuinness predicted that after the May elections, the party would be engaged in "some of the most difficult negotiations" it had ever faced.
"If these are to be successful, republicans must be honest in our analysis of the crisis in the peace process. But we also have to look to the future and set out clearly our solutions and our vision.
"As we look across a century of struggle, we see that each phase of the journey has been different. Each has required different strategies and tactics. Republicans required courage to survive, resourcefulness to find new ways forward and determination to persist with their course of action."
Mr McGuinness claimed that in every generation of struggle against British occupation, the "policy of criminalisation" had been introduced in an attempt to break the spirit and sap the energy of Irish republicans.
"Character assassination was used by the British against those Irish patriots who chose peaceful means of resistance, just as effectively as physical assassination was used against those who used armed struggle," he said.
