The study calls for better outdoor facilities for children

Playing pirates, princesses or mums and dads can be very good for a child's development, says Dr Sue Rogers of the University of Plymouth.

But she found the set-up and demands of the classroom mean opportunities for such role-play are limited.

The government insists young children in school are learning through play.

Dr Rogers studied 144 four and five year olds in three areas of south-west England in a year-long study funded by the Economic and Social Research Council.

She watched children in reception classes doing role-play games and canvassed them on what they liked to do.

Dr Rogers found that the classes were not always designed to meet their needs.

We would like to see less emphasis on keeping small children focused on classroom working Margaret Morrissey, National Confederation of PTAs

"'Children of this age learn to make friends as well as to use their imagination through role play," she said.

"We know that they are capable of sustained and complex imaginative play and that capturing and engaging their interest is essential.

"Unfortunately, pressures on time and space, as well as the need to teach literacy, means that playing at shops, pirates and hospitals is difficult to fit into the timetable."

She said children were often frustrated to be called away from a game with their friends to do more structured school lessons.

Boys might find their games are seen as too boisterous for the classroom setting.

The children's games tended to follow gender patterns, she said, with girls often opting for a nurturing-based game such as mum and baby, while boys were more interested in being action heroes, despite teachers' efforts to 'de-gender' role play.

Outdoor space

Her report says role play is valued highly by both children and adults and that it can make "a significant contribution" to learning and development.

"However, the intervention of certain pedagogical factors often prevents children from realising its potential."

It suggests there is a need for more outdoor play spaces so that children could have more choice over materials, locations and playmates.

This could encourage girls to take a more active role in building activities and allow boys' play to develop without disrupting people around them.

A spokesman for the Department for Education said: "It's completely wrong to suggest that children are missing out due to the national curriculum.

"On the contrary, the foundation stage for three to five year olds is all about learning through play with enjoyment and challenge - enabling children to develop the key skills needed for all future learning."

Margaret Morrissey, from the National Confederation of Parent Teacher Associations, said many parents were concerned about a lack of play in school.

"We would like to see less emphasis on keeping small children focused on classroom working," she said.