The Green Party has lost its minority control of Brighton & Hove City Council to Labour in polls held on the same day as the General Election.
Labour is now the largest party, gaining minority control with 23 seats, five short of an overall majority.
The Conservatives have 20 seats while the Greens, who lost nine seats, now have 11.
Brighton & Hove made history in 2011 after becoming the UK's first council to be led by the Green Party.
At the time they were elected on a promise to "resist the cuts" but since then the city has suffered "unprecedented" cuts of £80 million
Labour group leader Warren Morgan tweeted: "When I welcome the @UKLabour conference to Brighton and Hove in September, I can honestly say that the fightback started here.
"I am proud beyond words to be the leader-elect of Brighton and Hove City Council - the place I have called home all my life."
Tom Druitt, chair of Brighton and Hove Green Party, said: "We have protected public services and kick-started regeneration in the city".
He said the election "was always going to be difficult" but he was pleased the party had 11 Greens elected "so we remain a strong voice on the council".
He promised to continue to "challenge others whenever they fail the people we represent".
The party's performance in the General Election was described as the "most successful" ever by MP for Brighton Pavilion Caroline Lucas.
Ms Lucas became the Green Party's first MP in 2010 and held her seat this time with an increased share of the vote.
Geoffrey Theobold, of Brighton & Hove Conservatives, said: "We were pleased to gain two extra seats on the council, which remains very hung. But we are disappointed that the Labour party now has three more seats than us and will lead the administration.
He added: "We will remain a constructive opposition."