The appointment is part of a restructure at Southwark that has already delivered nearly £400,000 in savings.
Southwark Council said the restructure of its comms and cabinet office teams was designed to reduce costs to help meet its savings targets and to reshape its external affairs to become more strategic and include a new policy and public affairs function.
It is designed to deliver savings of 25 per cent and reduce the team's headcount from 32 to 21.
Manwaring, who takes up his new role this week, joins the council from the Chartered Institute of Management Accountants (CIMA), where he was executive director of external affairs.
His previous experience includes eight years as the chief executive of think-tank Tomorrow's Company, which promotes purpose-led business.
Before this, Manwaring had long stints in the charity sector, including as chief executive of disability charity Scope and director of external affairs for Action for Children.
He was also head of the general secretary’s office for the Labour Party, for ten years and a Cambridge scholar with an MA in economics.
Manwaring said: "I'm thrilled to join Southwark Council at such an exciting time for this dynamic borough which is filled with opportunity. I believe there is great potential for us to deliver even more for residents, not only by making sure they are aware of all the fantastic things on their doorstep, but also by championing their cause.
"I'm looking forward to working with some great people to help tell Southwark’s outstanding story."
Councillor Peter John, leader of Southwark Council, called Manwaring’s appointment a "coup" for the borough and said that his breadth of experience would help the local authority "challenge how we work".
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