A quarter of Irish three-year-olds are now overweight or obese.

The latest Growing Up in Ireland study of 11,100 infants found that while 5% of chldren in the most socially advantaged group are obese, that figure increases to 9% among those who are most disadvantaged. 

The study revealed that harsher parenting styles are related to behavioural difficulties in children while cognitive ability is strongly linked to the mother's education level and how often she reads to her child. 

It also showed that the recession had a "significant or very significant impact" on almost two-thirds of families with three-year-olds.

But the vast majority of infants were found to be in good health, with 98% of parents describing theirs as "very healthy or healthy". 

Minister for Children and Youth Affairs Frances Fitzgerald noted the emergence of a social gradient, saying the findings "remind us of the important role for public policy in mitigating the effects of early disadvantage".