The authority wants to designate all its pre-five establishments as early education and childcare centres, which the GTC fears might downgrade the role of education and therefore teachers.
West Dunbartonshire's education committee decided last week to press ahead with its plans, which it believes are necessary to provide a more flexible service for parents.
The present system of schools, community nurseries, family centres and day nurseries separates education from childcare and, the council says, parents have been demanding change.
Danny McCafferty, the council's education convener, said they would met GTC concerns by having a peripatetic head who would co-ordinate all teaching staff. The frontline teaching service would be increased by 50 per cent, he added.
But Tony Finn, the GTC's education convener, told the council last week: "There has to be a balance between a requirement for good childcare and good quality education. At a time of limited resources, that's quite difficult." Unless a school was appropriately staffed and managed by those with appropriate educational qualifications, Mr Finn warned, "standards could, and I stress could, be put at risk".
A report to the GTC expressed fears that the redesignated centres would no longer be seen as schools, would not necessarily be led by a headteacher and teachers would not always be appointed to all establishments. The move was therefore a "retrograde step".