A growing number of schools have scrapped the traditional Mary and Joseph performances in favour of secular alternatives such as Snow White or Scrooge.
Others have removed explicitly religious messages from their re-enactments of the birth of Christ for fear of upsetting pupils of other faiths.
Now vicars have spoken out against this watering down of the nativity, complaining that children are not being taught the spiritual message of Christmas.
"I have seen performances where the central character has not been Jesus. Instead he is replaced by an angel or a sheep, and I think that's a shame," said Rev Roger Widdecombe, vicar of St Paul's in Cheltenham, Gloucestershire.
"I'm a big fan of keeping the nativity as a nativity, although I realise the performance has to engage youngsters and there aren't that many well-written nativities out there."
Recent Christmas plays put on by schools near Rev Widdecombe's parish include Jack and the Beanstalk, Whoops a Daisy Angel and The Grumpy Sheep.
The latter tells the story of a lazy, cantankerous sheep who develops a more cheerful personality after travelling to meet Jesus in the Bethlehem stable.
Last week retailers reported that parents are ditching homemade nativity play costumes and spending up to £150 on "manger chic" designer outfits.