"One size no longer fits all," he will say. "Charities have developed significantly since they were first regulated 400 years ago.
"Our governance structures have remained largely static. Charities need to be freed up to experiment and to choose different ways of operating."
Unlike public and private sector organisations, the directors of charities, including chief executives, do not have voting rights and often do not sit on the board. Some charities such as the Scout Association have successfully applied to the Charity Commission to include executives on their board, but many have had requests turned down.
In a report, Rethinking Governance, to be presented at the conference, Acevo says that a relaxation of the rule would make charities, especially those that have contracts with local authorities, more accountable. Issues could be raised immediately without waiting for trustee meetings.
"Current governance arrangements with wholly non-executive boards suit many third sector bodies," Bubb will say. "But others need a different structure, particularly those that have developed significant trading roles."
The report, which presents the results of Acevo's governance inquiry, states that diversity is a major problem for charity trustee boards. The survey also discovered that skills, such as marketing, human resources, IT and fundraising are not represented on half of all boards.