The Green Party is celebrating after doubling its number of councillors in Brighton and Hove from six to 12.
Green Party speaker Sian Berry said they had benefited from Labour
Spokesman Keith Taylor said he was pleased the party had won seats in a part of the city that David Cameron was campaigning in only two days ago.
The Greens also won an extra seat in Norwich, meaning they now have 10 councillors in the city.
The party had set a target of gaining 30 seats and 10% of the vote in areas where it is standing.
Leaders said they were hoping to capitalise on the major parties talking about green issues.
Sian Berry, Green Party principal speaker, said current councillors had shown it was worth voting for the party.
"They are showing what Green can do when they get elected," she said.
"Our councillors in Norwich are doing a great job. Our councillors in Kirklees similarly have done an amazing job and have turned Kirklees into one of the greenest places in the country.
"So it is worth voting green in the local elections. We are hoping to, and we almost certainly will, break through the 10% barrier in every place we stand."
The party, which said it fielded 1,400 candidates in England, gained an extra councillor in Kirklees, boosting its numbers to four.
In Brighton and Hove, Conservative Steve Strange unseated Sue John, deputy leader of the Labour group.
The council remains under no overall control, with the Conservatives securing 26 seats, Labour 13, Greens 12, the Lib Dems two and one Independent.