SDLP MLA Colum Eastwood says the party will support their new leader “to the hilt”.
Mr. Eastwood - who previously withdrew from the race for the party’s deputy leader role - welcomed Alasdair McDonnell’s election.
He said: “We’d four very good candidates, we’ve one very good leader and we’ll all back him to the hilt.”
Dr. McDonnell saw off three other candidates at the SDLP conference to succeed Margaret Ritchie.
The new leader of the SDLP has set a target of 20 seats for the party at the next Assembly election arguing that the party has suffered at the polls in recent years because it had been too focused on implementing the peace agreement.
“What has gone wrong is that we have put far too much of our energy into supporting the settlement, we have been supporting the implementation of the Good Friday Agreement,” he said.
“That has been our focus, we have almost been hypnotised by it and we have neglected our grass roots. I want to go back to taking care of the grass roots.”
Mr. McDonnell told his party conference that his leadership of the SDLP will signal a new era for politics in Northern Ireland.
He also accused Sinn Fein and the DUP of presiding over cuts demanded by Westminster.
The two parties, he said, were “bailiffs for the absentee landlords of the Treasury”.
He said the SDLP had put too much effort into providing a “comfortable place for other others around the Good Friday Agreement” to the point where his party had become “hypnotised” by it.
“We must face up to the reality that the agreement has been left by the DUP and Sinn Fein to run out of road,” Dr McDonnell added.
“In the hands of the DUP and Sinn Fein, it may provide basic political stability but it will not deliver the real progress that we want to achieve.”
He also set out plans to set up a “small expert commission” which would be tasked with improving the organisation of the party.
Poking fun at the characterisation of him as a “bull in a china shop”, Dr McDonnell said that he took the analogy as a “tribute to my reserves of energy and passion, tempered with wise counsel”.
He added that he wanted to “smash the myth that the SDLP’s fate is already sealed, that this party is somehow doomed to fail and die”.
“All that is wrong with us is that we don’t get enough votes - that is all,” he said.
Meanwhile, former party leader and local MP Mark Durkan told the weekend conference that changes in policing have made a positive difference.
Commenting on the 10th anniversary of the PSNI, Mr. Durkan said: “This would not have happened and succeeded in the terms that it did had the SDLP not made the running first of all in securing the establishment of the Patten Commission and then taking the lead on driving the implementation of Patten and its delivery through the Policing Board.
“We should acknowledge the work and worth of the Patten Commission itself and their definitive recommendations which were clearly-thought and well-calibrated in spite of the criticisms to which they were subjected to at the time.
“Whatever about commentator criticisms of the Policing Board’s role more recently we also need to acknowledge the significant contribution of the Patten-modelled board in overseeing change and transcending vexed differences.”
Mr. Durkan added: “The SDLP and its representatives were there for all the big challenges and the big choices when it mattered and when it wasn’t easy.
“Credit is also due to the calibre of leadership within the PSNI who took the opportunity of a changing environment to affect significant change in attitudes within policing and about policing.”