Pembrokeshire's Assembly Members are concerned about an apparent "done deal" which will see the new super health trust based in Cardigan.
Health minister Edwina Hart has written to Cardigan's AM Elin Jones saying: "I have discussed the siting for the new headquarters with the chairs of the existing trusts, including my thoughts that it could be located in Cardigan."
Angela Burns and Paul Davies, Assembly Members for Pembrokeshire, are worried that a full and fair inquiry into the best location for the Hywel Da Trust headquarters has not been held.
"I am concerned that Ms Hart favouring Cardigan means that this is effectively a done deal," said Preseli Pembrokeshire AM Paul Davies.
"We must make sure that all the options are looked at and this move makes economic sense."
His South Pembrokeshire counterpart Angela Burns is concerned that building new offices in Cardigan is not the best solution.
"I strongly feel that the new trust should be based at one of the existing three trust offices. The whole point of this exercise is to save money and this will not happen if they start building or renting new offices.
"Why not have a split site? Plenty of businesses already do this thanks to modern technology and the new trust does not have to be in just one spot.
"You could have the finance department in Carmarthen and the human resources department in Cardigan. This would also help to retain many of the existing staff.
"I also believe that the new offices must be based at the sharp end - in other words the hospitals - so that they won't get divorced from the reality of providing health care."