Ms Bríd Rodgers, in her last SDLP conference as an elected representative, said the clearest sign that the IRA was totally committed to peace would be through Sinn Féin joining the Policing Board.
The SDLP deputy leader said at the opening of the 32nd annual party conference in Armagh last night that while Northern Ireland was currently gripped by political uncertainty, it was not a "major crisis", and the problems could be overcome.
The former agriculture minister is not standing in the next Assembly elections - if they are held - and will stand down as deputy SDLP leader at the conference next year. In a detailed speech last night, she turned her ire on republicans, loyalists and unionist politicians, while pledging that the SDLP "would always put people before narrow political advantage".
Ms Rodgers said republicans were hindering unionist endorsement of the Belfast Agreement. "Let me say to Sinn Féin that when you talk of reaching out to the unionist community, of understanding their fears, whilst threatening a unilateral takeover on the basis of headcounts with slogans such as 'greening the west', you are undermining the pro-agreement unionist constituency.
"This language, coupled with the alleged activities of the IRA, has eroded the confidence of that constituency for our new institutions. I know it because I talk to them," she said.
She urged republicans to take action to generate universal support for the Good Friday accord. "They can listen for a start to what the people of Ireland demand. Stop the punishment beatings, the summary justice, the community control. Stop the double speak and the blame game," she exhorted.
"They can take heed of the Irish News, a paper that has been steadfast in its support and encouragement for the republican movement in its transition from violence when it said on the 8th of October this year, and I quote: 'What needs to be recognised by republicans is that maintaining a private army and holding seats in government are incompatible in every respect'."
She added: "When Sinn Féin shows (it is) willing to face up to the challenge of providing a representative, accountable and effective policing service for all the people of Northern Ireland, this will be the clearest possible signal that the war is truly over and that all engaged in unaccountable community control are being stood down once and for all. I call on Sinn Féin to take that step now."