Oxfordshire County Council and Cherwell District Council have agreed to extend the arrangement under which they share a chief executive and some services, with proposals for a shared law and governance service expected to come forward this month.
The two began their partnership last year and said it would yield savings of £620,000 in 2019-20.
They are also exploring joint working in corporate services, policy and communications, human resources, finance, housing, regulatory services and family safeguarding.
In addition to the chief executive, four other senior posts are shared and more may follow.
Shared assistant chief executive Claire Taylor said: “Cherwell District Council has a track record for innovation in housing and regeneration and Oxfordshire County Council has a proven history of attracting infrastructure funding linked to housing to improve our transport network and other essential public services.
“Our ambition is to maximise those skills, resources and national funding to make the housing and economic growth planned for our county work to the benefit of everyone in our towns and villages.
“The way we manage this growth can only benefit from ever closer working between our two councils.”
She said the two authorities’ ambition was to “trigger a broader conversation throughout the country about how the councils and other public bodies can work better together”.
Cherwell and Oxfordshire is one of few examples of ‘vertical’ integration between a county and a district, rather than between councils at the same level.
Other examples exist with North Yorkshire and Selby and Gloucestershire and Gloucester, though a similar arrangement between Essex and Brentwood was abandoned in 2012.