Nurseries and other childcare providers say plans to allow more children for each member of staff in England will not cut costs for parents.
Most nurseries and pre-schools were opposed and would not increase numbers, the Early Years Alliance charity said.
One mother, whose two-year-old has severe allergies, told BBC News she did not want staff stretched further.
The government said it would consult on whether to allow each member of staff in England to look after more children.
Currently, in a nursery in England, one adult can look after four two-year-olds.
In Scotland, five are allowed.
The government is to ask parents and childcare providers' views on whether to do the same in England.
