A council by-election will take place alongside the General Election after the resignation of Clissold ward councillor Ned Hercock for personal reasons.
Labour's Cllr Hercock served for five-and-a-half years but has vacated his seat with immediate effect.
"I'm standing down for personal reasons," he said. "I'm very proud of what's been achieved in that time by the mayors, their cabinets, and the wider team of Labour councillors.
"The borough has great officers who work hard to deliver these aims, and a public who support the vision of a fairer, greener, more liveable city. I love Hackney and its people, whom it has been a great privilege to serve."
Candidates for the by-election will be selected in the coming days. The winner will join Clissold's two Labour councillors Sophie Cameron and Sade Etti.
"We wish Ned well and thank him for the service he has given Hackney," said Cllr Ian Rathbone, chair of Hackney Labour group of councillors.
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