Sending very young children to inadequate day nurseries could lead them to develop behavioural problems, a group of childcare experts has warned.
Some nurseries fall short in the day-care provisions, it is claimed
In a letter to the Daily Telegraph they call for an "urgent national debate" to ensure children with working mothers receive the most appropriate care.
They accept many nurseries strive to provide "continuity in personalised care-giving" but say many fall short.
The government said early years provision could benefit children.
An education department spokesman said parents "should have a choice about how they balance work and family life".
"If they choose childcare, they should be able to do so with confidence."
Signatories to the letter included academics, authors and former teachers.
It stated: "Consistent, continuous care by a trusted figure is the key to providing a secure and nurturing environment for very young children.
"Research suggests that its absence can lead to behavioural difficulties in children as they grow older."
Author Sue Palmer, who signed the letter, told the BBC that during the first six to nine months of their lives children needed to develop a "secure attachment".
This attachment should be to "one person in their life who they know they can trust, who will be there for them all the time and isn't going to go away".
"If the child is securely attached then quite often they make lots of other attachments to other people and can be quite happy going off to nursery," she said.
Research carried out by Sir Richard Bowlby - another of the letter's signatories - suggested about 40% of toddlers in the UK and US did not develop this secure attachment.
Ms Palmer added: "One of the problems with institutionalised care is very often there's a lot of different people, so the child doesn't know that there's one there that's especially for it."
Sir Richard told the Telegraph the government should not encourage mothers back to work by funding day-care schemes until a proper discussion has been held.
"The government should make it easier for parents to use their child-care allowances to pay a grandmother or other relative to look after their children," he said.
A spokesman for the education department said care provided by family members was valuable but it would be "inappropriate for government to interfere in these private arrangements".
"To fund this sort of care would mean assessing its quality and nobody would want to see grandparents being inspected by Ofsted."
Other signatories to the letter included actor Tom Conti, Professor Allan Schore from the University of California and Steve Biddulph, author of Raising Babies.