All primary schools should hold a nativity play regardless of the religion of their pupils, according to the equality chief Trevor Phillips.
Trevor Phillips says the nativity play is part of what it is to be British
Last week, a Sunday Telegraph poll indicated that only one in five primary schools was planning a nativity play.
Mr Phillips, chairman of the Commission for Equalities and Human Rights, told BBC Radio 4's Today that schools should not shy away from the Christmas story.
He said it was a "very important fundamental, national celebration".
A growing number of people are unaware of the Christmas story, according to the public theology think tank Theo.
It carried out a poll which suggested that 27% of people are unable to identify Bethlehem as Christ's birthplace and that number rises to 36% of people aged between 18 and 24.
'Robbing their children'
Mr Phillips said he was concerned schools were not putting on nativity plays because pupils may not be Christians or because they belonged to other religions.
Mr Phillips said he felt this meant that today's children were missing out on a very British tradition.
"Schools which are deliberately shying away from the true story of Christmas are just plain wrong," he said.
He added: "What they should do is make sure that all of their children have access to this very important fundamental, national celebration and tradition.
"Otherwise they're robbing their children of really being part of what it is to be British."