By Sean Coughlan
BBC News, ATL conference in Bournemouth
The Education Secretary Alan Johnson has said it is "ludicrous" to believe that mothers going back to work could damage their children.
"Ludicrous to say children would be damaged," said Mr Johnson
This follows research for the Department for Education and Skills linking long hours in childcare with increased anti-social behaviour.
Mr Johnson was addressing a teachers' conference which had heard warnings of the "institutionalisation" of children.
Work hours and full-time childcare were destroying family life, said teachers.
The research published by the DfES found that children spending more than 35 hours per week in a nursery were more likely to be "anti-social, worried and upset".
But Mr Johnson, speaking to journalists at the Association of Teachers and Lecturers in Bournemouth, defended the importance of providing childcare that allowed parents to return to work.
The government is promoting the idea of "extended schools", which will provide after-school classes and a safe childcare environment for working parents.
But teachers at the conference expressed fears about the long-term impact on family life when children spent so much of their time away from the parents.
Cecily Hanlon from the Childcare and Early Development Centre in Leeds challenged the "long hours culture" that was now being experienced not only by parents, but by their young children.
Babies and toddlers were now spending 10 hours a day, five days a week in institutional childcare, she warned.
"They can spend their whole childhood in care. It's a tragedy for the child and for the family," she told the teachers' conference.
While there was rhetoric about "family-friendly jobs", the reality she said was that people were forced to be "job-friendly families".
Spending so much time away from their own family meant that children were increasingly influenced by their peer group, rather than adults, she said.
And Ms Hanlon called for more research into whether such a weakening of the links within families was contributing to more aggression among youngsters.
"It's about opportunities," says Alan Johnson
"As a society, are we going to reap the whirlwind?" she asked the conference.
Teachers, while defending the importance of childcare, also pointed to the economic reality facing many families with young children.
With the need to pay such huge mortgages, the one-income family was no longer feasible, said one teacher. As such, there was little option for parents other than to work long hours and for their children to spend even longer days in childcare.
Another speaker criticised the culture of "wrap around care" when it "should be the parents wrapping their children in their arms".
But the education secretary said that improving and extending childcare was an important part of giving more options to families - along with measures such as longer maternity leave, paternity leave and flexible working.
He pointed to the example of Finland where high-quality childcare from an early age was a successful part of a high-achieving education system.
"It's about giving parents opportunities so that they can combine their working lives with their family lives," said Mr Johnson.
"The idea that somehow women going back to work are letting down their children is frankly ludicrous."