The Local Government Association is calling for membership of care trust boards to be based on a principle of equal representation for health and local government.
It is making the call in a hardening of its position on the new organisations as part of a drive for 'series of principles on which we think care trusts should be based' .
Head of social affairs John Ransford said: 'The principle is equal representation between members of local authorities, and health non-executive directors and also between professionals from the local authority and from health.'
Although in some instances there might be 'more from the local authority' or 'more from health', balance was the key, he said.
The LGA will be pushing for local flexibility in care trust arrangements as the Health and Social Care Bill goes through its committee stages.
'We are afraid that the bill may lead to a restrictive model, ' Mr Ransford said.
The association is also concerned about the proposal to give the health secretary powers to impose care trust status where services are 'failing'.
'One of the implications of the bill is that failure would be on the local authority side and you'd use a care trust to solve it, ' he said.
The government needed to 'define what is success and what is failure and set some criteria', Mr Ransford said.
'You would need a pretty serious level of failure to justify an organisational change.'