I’m simply informing you of fact, if you feel that you know better than that is up to you. HOWEVER I am informing you that my education and career is legal. If you have equal knowledge (in this case you clearly don’t) then great. However I’ve always been taught to respect where people know best.
The council is NOT the data controller. As grey an area as GDPR is, it is not difficult.
The law states that ONLY necessary information should be shared with ONLY the necessary parties.
Therefore a person complaining about about bin emptying for example should NOT have their email address, home address or telephone number shared, it is unnecessary!!
If a complainant provides name, address etc etc and is complaining about the councils objection to their planning application and you have a complaint committee AND planning committee then could argue that each committee can have access to the details as it could be deemed necessary.
As I said it really, really isn’t hard.