Deputy First Minister Martin McGuinness has warned that the Stormont Executive lacks cohesion and has blamed unionists for the problems, questioning their commitment to being in Government with him.
He said he believed this instability at the heart of the administration is holding up decision-making and making it harder to resolve disputes over issues like loyal order parades and flag-flying.
The Deputy First Minister made his comments in a keynote address last night at his party's ard fheis in Castlebar, Co Mayo.
His theme was "15 years on from the Good Friday Agreement".
In a pointed reference to Peter Robinson and the DUP ministers, he said "all of this would be helped greatly if some within unionism ended the pretence that they are not working the Good Friday Agreement institutions".
The DUP opposed the Good Friday Agreement and Mr Robinson recently claimed that the party changed it out of all recognition in the St Andrews Agreement of 2006. Mr McGuinness made no secret of his contempt for this analysis.
"People need to be in Government not because they have to be but because they want to be – and approach decision-making in that spirit," he said.
He told a hall peppered with IRA veterans "it should not be forgotten that it was the leadership given by Irish republicans, leadership for an end to conflict and for peace, which made all this happen".
He said the Good Friday Agreement "would allow us as Irish republicans to map out very clearly a peaceful and democratic path to a united Ireland, it would enshrine in law the rights of citizens in the North to our Irish identity and offer the same checks, balances, rights and responsibilities to the unionist people also".
Mr McGuinness said: "More than once in recent months the observation has been made to me that Sinn Fein ministers are in Government with unionist ministers because we want to be, but that unionist ministers are in Government with Sinn Fein because they have to be.
"Speaking frankly, this isn't good enough."
He accused unionists of not showing respect to nationalists.
"I have no difficulty whatsoever in respecting unionists' allegiance to their Britishness – but it gives me no satisfaction to tell you that there is a marked reluctance by unionist leaders to respect the Irish identity of nationalists and republicans," he said,
"This difficulty goes to the very heart of the failure to resolve contentious Orange parades and the need to ensure that symbols and emblems on the basis of equality reflect the allegiances and identity of the community as a whole."
He also attacked Prime Minister David Cameron, who he said had failed to deliver the promised economic peace dividend to Northern Ireland.
Mr McGuinness said both the British and Irish governments had adopted "a semi-detached approach" to Northern Ireland and their commitments enshrined under the Good Friday Agreement.