SDLP councillor Paul McCusker has announced he is to quit the party.
In a statement, he said he would be "best placed to run as an independent in the upcoming council election" in May.
Mr McCusker, who has been an SDLP councillor for Oldpark since 2016, said he had become "frustrated and disheartened" with politics at a central and local level.
He informed the SDLP of his decision on Wednesday.
Mr McCusker previously served as deputy lord mayor of Belfast. He also founded the St Patrick's Soup Kitchen in 2017 and campaigns on issues regarding homelessness, poverty and addiction.
In a statement posted on his Facebook page, he said: "I have been undecided on what to do regarding my political future as it’s been a challenging year for me, I have decided that I would be best placed to run as an independent in the upcoming council election.
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"I honestly have been left frustrated and disheartened with politics at central and local level on the lack of progress on issues that I am very passionate about.
"Issues such as addiction, homelessness and poverty continue to impact on the lives of individuals and families who I support and I will continue to highlight and lobby on behalf of those who experience these issues if elected in May."
He added: "We have continued to see year on year very little focus on the important issues that I highlight resulting in more deaths, lack of suitable services and people plunged into despair and misery, it is very difficult to sit back and watch this not get the political attention it deserves.
"Continuing as an independent will allow me to give a voice to those who often feel forgotten and continue to fight for better services."
An SDLP spokesperson said the party was disappointed Mr McCusker was "stepping away".
"It's been a tough time for him but we've really enjoyed working with Paul and he'll continue to have friends in the SDLP who wish him well in the future," the spokesperson told the BBC.
"The SDLP will be making an announcement about additional Belfast City Council candidates shortly."
