There were 89,000 votes in favour of switching to committees and 48,000 votes to remain with the existing system.
A Cabinet will remain for the next year while there is a gradual move to committees. The number of committees, how they are made up and how they will operate still needs to be thrashed out.
The council is now in no overall control following Labour's defeat at the local elections. No one political party has a majority so there will need to be a coalition.
The referendum was sparked by It's Our City campaigners.
More to follow.