A DUP spokesperson thanked Guy Spence for his service.
A Belfast councillor has resigned from the DUP, saying he has "lost all confidence" in the integrity of the party.
Former Deputy Lord Mayor Guy Spence issued a statement saying he is resigning from the DUP and retiring from his position on Belfast City Council.
In a statement posted on his Twitter account, Mr Spence said his resignation had been accelerated by "recent events."
"For the last year or more I have been wrestling with my conscience watching party values and integrity be tossed aside often by personal agendas for individual gain," he said.
"I have lost all confidence in the party, in particular its integrity, making my position within it untenable."
Mr Spence said that he had written to the chief executive of Belfast City Council to inform her that he will be retiring from the local authority at the end of this month.
He added that he plans to step back from politics and pursue a new career.
"Until then I will be an independent member of council," he said.
"My resignation and retirement has been accelerated by recent events involving a blatant attempt to cause me harm. Something I'm not prepared to tolerate.
"It has been a privilege to serve the people of Castle District, the place I call home, for the last nine years.
"I want to thank every single person who supported me throughout my time in Council and everyone I've had the pleasure to work with."
In a statement, the DUP said: "The party thanks Mr Spence for his service as a councillor.
"We will be co-opting his replacement in due course."