Australian children are spending, on average, almost an entire day of the week on their smartphones.

Research released by Telstra on Monday says that more than two thirds (68 per cent) of children aged three to 17 own a smartphone and an average of 21 hours and 48 minutes per week is spent on the devices.

Last chance: the Samsung Galaxy S6 Edge. Credit:Reuters

The online survey of 1365 parents concluded that their top concerns involved the time-sapping power of phones and risks around cyber safety and sexting.

However, while two-thirds of the parents said they had discussed usage guidelines, a quarter reported difficulties carrying them out.