Councils, MPs, MEPs, business and the voluntary sector will be asked their views on holding a vote to set up the assemblies, said local government minister Nick Raynsford.
Mr Raynsford is to seek views about the shake-up of local government which will accompany the setting-up of any assembly, in which county councils are scrapped and replaced with unitary authorities.
The minister said he wanted a structure which can deliver Whitehall's modernisation plans. This should be considered by the Boundary Committee when it draws up its map of post-assembly councils.
Mr Raynsford again insisted elected assemblies would not be forced on regions.
'We have no intention of forcing elected assemblies on any region. We believe people should be given the opportunity to make that choice,' he said. 'Fundamental to this process will be the level of interest in each region in holding a referendum.'
But shadow local government minister Eric Pickles attacked what he said was asking 'the same old suspects' what they thought about a referendum on a regional assembly.
'What you've got to understand is that this is a joy-ride for the political classes. The prospect of finding out what ordinary voters think is of no interest to the government.
'This is a great piece of candyfloss for politicians to gorge themselves on. There should be proper consultation with voters, not asking some old MP or MEP if it would be nice to find them somewhere to while away their twilight years.'
The deadline for responses to both the soundings exercise and the consultation on the draft guidance is 3 March.