Local government bosses have accused the Welsh Assembly government of undemocratic behaviour over planned cuts to the number of council representatives on NHS boards.
Councils are used to having several representatives on 22 local health boards, which largely share boundaries with local authorities.
But in the proposals under consultation the boards will combine with provider trusts into seven new boards covering much larger areas but with only one councillor each.
The existing boards are considered to be good at joint working, with strong accountability and public involvement.
Nineteen community health councils, well regarded for promoting involvement, will merge into seven, sharing boundaries with the new boards, with 23 new area associations working under them.
Welsh Local Government Association director for social services and health improvement Beverlea Frowen told HSJ some councils were willing to find partnership arrangements, but there was widespread concern about the plans.
"Seven into 22 doesn't go. If you take the case of North Wales you are asking six councils to nominate one [representative] and that does not chime with them being democratic sovereign bodies."
The proposals also say a council social services director should take a non-voting role on the boards. But councils say they should be able to decide which of their officers takes the position, Ms Frowen added.
Board chairs said they could understand the councils' concerns.
Cardiff local health board chair Fiona Peel said: "Having had a strong period of local accountability the authorities feel the new boards disempower them."
Another board chair told HSJ that the voluntary and charity sector may also feel under-represented.
"Joint working with the local authority has improved significantly over the past few years," he said. "I think members [of the existing local health board] are concerned about localism and the relationships that have been established."
Health minister Edwina Hart has said the reorganisation will "reinstate democratic engagement at the heart of the Welsh health service".