He is due to spell out his blueprint for local government reform in Scotland during a speech to the Convention of Scottish Local Authorities in Edinburgh today.
The changes are not expected until after the Scottish electorate votes in the next local elections on May 6 next year but they should be in place for the following elections.
Mr Dewar will tell Cosla: 'Only by modernising can councils lead their communities effectively and provide efficient local services.
'People need to know who is responsible for running local services. Councils need to be accountable to the public and the voters.'