Following his suspension, the SDLP launched an investigation, which subsequently concluded with Tierney’s reinstatement in April 2025.
In his statement on Wednesday, Tierney made no reference to the controversy over his reference for the soldier but said it had been a “huge honour” to represent the people of Derry.
“There’s no greater honour than serving the community you live in and the people you live alongside as a political representative,” he said.
Tierney said it had been his “personal and professional privilege” to represent the people of Ballyarnett for almost 14 years and to have had the opportunity to serve as mayor.
But he acknowledged that being a full-time public representative was “a tough balancing act” and he had been reflecting on his position over recent months.
“For a variety of reasons, I’ve decided that this is the right time for me to stand aside. I therefore will not be contesting the next election and plan to stand down from the council early next year,” he said.
Tierney said he first put his name forward for election in 2013 because he wanted to improve the lives of his neighbours, deliver for his community and “stand up for the city I love”.
He said he was proud of what he had achieved alongside his SDLP colleagues, representatives from other parties and community activists across the city.
Tierney also paid tribute to his family, saying his wife Cheryl, their children and wider family had put up with “summer nights spent knocking doors, lost weekends helping people with their problems and all the challenges that the families of politicians have to put up with”.
In a statement, Foyle MP and party colleague Colum Eastwood said Tierney had been his “right hand” for as long as he had been in politics.
“Throughout that time, he has been incredibly loyal, always going above and beyond,” Eastwood said.
“Nothing has ever been too much for him.
“He will be a huge loss to politics right across Derry and, in particular, to his constituents in Ballyarnett, who he has proudly represented with distinction.”
BBC News