Plans for a £15m mental health facility in Wellington are to be submitted as part of a regional strategy to have more than 130 psychiatric patients treated in the area.
The 75-bed unit at Westpark 26 business park could create 225 jobs.
Local councillor Ross Henley said he had "serious concerns" but the company behind the facility, Priory Group, said it would submit the plans in September.
Proposals for a similar 62-bed unit in Bridgwater have already been submitted.
They have been put forward by a separate company, Cygnet, and are due to be considered by Sedgemoor District council on 5 October.
NHS Somerset said only around five or six people from Somerset needed psychiatric treatment each year but the plans for these two facilities had been commissioned by the NHS South West.
Mr Henley said: "Wellington is the wrong location. We all know there has to be these types of facilities somewhere but I think in a built-up area like Wellington... no, I would not support this type of facility."
A Priory Group spokesman said the unit could bring in £5m in investment to the area annually.