Letters have been written to the Secretary of State for Health and Social Care, and to Thurrock MPs, raising serious concerns about plans by NHS England to merge Thurrock Clinical Commissioning Group (CCG) with 4 other CCGs in South Essex.
The action comes after it emerged NHS England has instructed the 5 CCG accountable officers to set out a clear and agreed timeline for a formal CCG merger by the end of September 2019.
Thurrock Council last week criticised the plans, which it fears would lead to the loss of local accountability and strong existing partnerships.
Cllr Sue Little, chair of Thurrock Health and Well-being Board, has now written to Thurrock MPs and Secretary of State for Health and Social Care, Matt Hancock MP, to outline the board's concerns.
Cllr Little said: "We have a responsibility to make clear our outrage at this decision, whether it is using our £490,000 to pay off NHS England debt elsewhere or trying to take our voice away for the services commissioned for Thurrock residents.
"This is an affront to Thurrock and one that we must stand up to and make clear that we do not support.
"We hope that by writing directly to our Secretary of State and Thurrock MPs Stephen Metcalfe and Jackie Doyle-Price our concerns will not fall on deaf ears and that we can work together on a solution that supports all CCGs in the region."