Mrs Spada (pictured), chief executive since 2006, tendered her resignation following a strategic review of the business.
The Chamber board, headed by president Silvia Vitiello, are supporting staff at the Chamber offices in Central Milton Keynes until a new chief executive is appointed.
They are also assisting in the development of a strategic plan as a foundation for long-term sustainability.
Silvia Vitiello said: “In a volatile financial climate, it is essential that the board of the Chamber of Commerce steps in to provide stability and enhanced service levels following the departure of the Rita Spada.
“Our Chamber sits at the heart of the community and our work is to provide businesses of all sizes, representing all sectors, with practical support, useful connections and valuable access to new ideas and innovations.”
She added: "There is a lot to do now and in the forthcoming year but, with the support of our current members and a drive to increase membership with improved services, we will be stronger and fitter to face the challenges ahead.
"We are grateful for the support of important, local business groups and working together we will make a real difference in the Milton Keynes and North Bucks area.”