Parents should think twice before allowing toddlers to play Angry Birds or other games on iPads or phones, it was warned after researchers found they were linked with poorer speech. Doctors found that toddlers in a clinic were often given smart phones to keep them occupied and investigated links to development and speech.

A survey of 65 families suggested most parents believed the games were educational and helping the child's development but this was not found to be the case.

The average age children starting using touchscreens was just 11 months and most used them for around half an hour per day.

The team from the Cohen Children's Medical Centre of New York found there was no difference in scores on general developmental tests in children aged up to three between those who played educational or non-educational games on touchscreen devices.

However those who played non-educational games such as Angry Birds or Fruit Ninja had lower scores in speech tests for both understanding of language and speaking.

Ruth Milanaik, chief investigator of the study, said: "We have observed in our neonatal clinic that the number one 'toy' parents are giving their toddlers are smart phones.

"It was striking to see that parents were substituting books and general baby toys for smart phones.

"Technology can never replace a parent's interaction with his or her child. Just talking to your child is the best way to encourage learning."

The researchers said they could not establish if the games caused poor speech or if children who were already struggling were drawn to playing those games.