Philip Parkin, general secretary of Voice, the union for education professionals said there has been a "downward spiral" in the quality of parenting and a disintegration of moral boundaries that would affect generations of children.
"The shortening of many relationships, the creation of more step-families, the emphasis on parents going out to work and the consequent perception of the reduced worth of the full-time parent have all changed the way we behave and the character of childhood," TimesOnline quoted Mr Parkin, a former primary school teacher, as saying.
Speaking at the annual Voice conference, he said that Government policies meant teachers were now responsible for children's weight and diction as well as stopping them joining gangs, carrying weapons and drinking alcohol.
He said many children live with "no functioning parent" in the home.
"There is no food in the house, no one washes your clothes, you don't get taken to the GP, the dentist or the optician," he said.
Mr Parkin said the commercialization of childhood made it much more difficult to be a parent than it was 30 years ago and he had "sympathy" for parents coping with these pressures.
A spokesman for the Department for Children Schools and Families said new plans mean that "parents will get more support and schools will have more services around them so that teachers are free to teach."