George Galloway's anti-war Respect coatlition has made significant in-roads in Tower Hamlets going from one to 11 seats.
Mr Galloway's party is the official opposition in Tower Hamlets
Respect are now the second biggest group on Tower Hamlets council.
The party unseated council leader Michael Keith but Labour is the biggest party in the East London borough and with 26 seats has retained control.
Meanwhile in Newham, Respect gained a third councillor. It also won a seat in Birmingham with 55% of the vote.
'Lib Dem collapse'
The Liberal Democrats, predicted by some to be the main challengers in Tower Hamlets, had a poor night compared with their expectations, ending up with four councillors.
A spokesman for Respect said: "The collapse of the Lib Dems and limited gains for the Conservatives, who went from one to seven councillors, means Labour could still retain control of the council, despite the repudiation of its controversial housing privatisation policy."
Labour MP Jim Fitzpatrick meanwhile said the party had been "improving services in recent years. I am delighted we have been given the chance to continue working for local people".
Mr Galloway helped found Respect: The Unity Coalition after being kicked out of the Labour Party.
Earlier this year he attracted criticism for taking part in Celebrity Big Brother, but defended his appearance, saying it presented an opportunity to raise his profile and that of his party among a younger audience.