Labour members of Brighton and Hove City Council want their political group to be known as the Labour and Co-operative group.
The name change was agreed at the same annual meeting of councillors that re-elected Gill Mitchell as the group’s leader.
The group said: “The Brighton and Hove group will be the first in the country to officially adopt the Labour and Co-operative title.
“Following last week’s elections, all Labour councillors in the city are now Labour and Co-operative members, so it was seen as the perfect opportunity to reflect this in the group’s formal title.”
The group said that the Labour Party and the Co-operative Party had run joint candidates since 1927, including former Brighton Pavilion MP David Lepper.
It added that there were currently 28 Labour and Co-operative sponsored MPs, including Shadow Chancellor Ed Balls.
Brighton and Hove Labour and Co-operative group deputy leader, Councillor Warren Morgan, said: “Following the local elections, we realised that all 13 elected Labour councillors were also members of the Co-operative Party so we felt the time was right to rename the group’s formal title to reflect this.
“There have been Labour and Co-operative councillors in Brighton and Hove for decades.
“David Lepper was a Labour and Co-operative MP for the city for over 13 years so this is a natural progression of a long tradition.
“There are dozens of successful co-ops in the city, as well as the familiar high street Co-operative businesses, and we hope to further reflect and represent those organisations and values in our policies in the future.”
Co-operative Party general secretary Michael Stephenson said: “I am delighted that Brighton and Hove now have a Labour and Co-operative group on the council and I certainly think it will be welcomed locally.
“At some point I hope Brighton and Hove will join councils like Lambeth and Oldham in having a Co-operative council.
“Brighton and Hove’s Labour and Co-operative group will now be on the forefront of promoting Co-operative Party policies based on democratic and mutual principles, which are more popular than ever, particularly in areas like fair trade, mutualisation of the banks, co-op schools and energy co-ops.”