Sutton Council leader Sean Brennan has announced he is stepping down after almost a decade in the role.
Councillor Sean Brennan, will step down from his post on May 21 when changes to how the council is run are brought in.
The Liberal Democrat group will elect his successor at their group meeting this weekend, with deputy leader Ruth Dombey expected to assume the role.
Coun Brennan, a former teacher first elected as a Sutton ward councillor in 1986 and who became leader in 2002, will still represent Sutton Central ward as a councillor.
Explaining his decision to step down, Coun Brennan said: "It’s been a real privilege to serve the community I have lived in for so many years and to meet such a wide range of dedicated and inspiring people.
"Throughout my tenure I’ve been struck by the incredible community spirit that we have in our borough.
"Whether it’s volunteering, helping neighbours, or having street parties, people want to know and help each other.
"I couldn’t have done my job without the help and support of local people, and I’d like to pay tribute to the many voluntary groups and partner organisations throughout the borough.
"Since I became leader almost a decade ago, the role of local authorities has grown whilst our government funding has been cut back significantly.
"Sutton receives one of the poorest funding settlements in London, but by being efficient and making savings we have been able to invest in jobs, community safety, schools and parks – whilst freezing council tax.
"It has been a period of significant change. All councils will be taking on new responsibilities in areas such as public health.
"With a new committee system coming into force in May, I strongly believe that this is the right time for a new leadership team to bring new ideas and new impetus to a changing and challenging environment."
The new committee system of governance - involving proportionate numbers of cross-party councillors in committees headed up by lead councillors- will replace the current cabinet system, where the council leader, deputy leader and eight decision-making executive councillors decide on council policy.
The Lib Dem choice for leader will be subject to a formal vote of all councillors at a full council meeting on April 30.
The council’s new leader designate will not adopt any formal powers until after the full council meeting on 21 May, when the governance system will be voted in.