Children who spend more than 35 hours a week at nursery show higher levels of antisocial behavior than those spending less time in daycare, according to government-funded research.

An evaluation of a £370m government scheme to expand childcare and encourage parents back to work found children were more likely to display antisocial behaviour the longer they spent in nurseries.

The study found positive as well as negative effects, however. Children appeared to gain in confidence, but those in daycare for longest were more "antisocial, worried and upset".

The study, based on profiles of more than 800 children and families at 100 centres, said: "Long hours in the nursery (more than 35 hours a week) had both positive and negative effects on children’s behaviour: they were more confident and sociable, but more antisocial and more worried and upset."

"The age at which children started nursery did not significantly affect their behaviour, but the more months they had been attending the more likely they were to display antisocial behaviour."

Children under three and a half attending nursery benefit from quicker mental development by mixing with older children, but were more likely to become upset, the researchers from Oxford University and the Institute for Fiscal Studies found. "While mixed age rooms may be better for young children’s cognitive development, they may not always be better for their emotional adjustment," the study found.

The researchers examined the behaviour of 800 children, recording instances of bullying, teasing, foot-stamping and bossiness, as well children becoming stressed by wanting more attention.

Children were less likely to be worried or upset in centres that were spacious and well-maintained. The report said: "Children in rooms with well-qualified staff, a good quality physical environment and a well-thought through structure to the day were less worried and upset and more cooperative and sociable."

However, the report said although the presence of a teacher was better for children "very few nurseries had teachers working directly with the youngest children".

The study evaluated the neighbourhood nurseries initiative, the scheme involving 45,000 children that is aimed at helping working-class parents, particularly mothers, into work.

The results, published yesterday on the Department for Education and Skills website, prompted a cautious response from professional childcarers. Purnima Tanuku, chief executive of the National Day Nurseries Association, said: "We hope that families are not needlessly worried by this report which only relates to behaviour difficulties in a small number of cases."

"Children from workless households were rated as less cooperative and sociable than children in centres with high levels of working parents. This indicates there is a complex mix of factors that influence a child’s behaviour and that careful attention is needed to ensure children are supported appropriately."

Publication of the research came as members of the Association of Teachers and Lecturers at their conference in Bournemouth debated the impact of childcare on family life. Some delegates argued that a huge increase in childcare and nursery provision was in danger of "institutionalising" babies and infants.

Teachers said well-meaning and lavish spending on under-fives, partly fuelled by a desire to encourage mothers into work, could be undermining family life.

Cicely Hanlon, of the childhood and early development service in Leeds, told the conference: "There seems to be an increasing conflict between the need/choices of parents and the needs of very young children."

Mothers not working "may have made an informed decision that staying at home is best for their own young family even though money is tight", Mrs Hanlon said. "It concerns me that with so many more children accessing childcare in groups, are we in the process of raising generations of children who are being taught their proper place in life is in fact with their peer group and not with their family?"

But Alan Johnson, the education secretary, said: "Any argument that there is evidence women are letting down their children by going out to work is faintly ludicrous."

Via the Guardian