Almost four million UK children do not own a book, research has suggested.
It raises concerns that the numbers of children without books is rising, with poor youngsters more likely to miss out.
The latest report by the National Literacy Trust, based on a survey of 18,000 youngsters, reveals that a third (33.2%) do not have books of their own.
It means 3.8 million UK children do not own a book, the trust claimed. And the number has increased from seven years ago, the last time the poll was conducted, when it stood at one in 10 youngsters.
This survey was based on a smaller number of children, around 8,000 in total. The report also reveals that boys are more likely to be without books than girls, and children eligible for free school meals - a measure of poverty - are more likely to not own a book than their richer peers.
The findings show that children who own books are more likely to enjoy reading, read more books and read more frequently and for longer. They are also more likely to perform better at school and to have visited a library or bookshop.
Just 7.6% of pupils who have books of their own are reading below the expected level, compared to 19% of those that do not own books, the report found. Researchers also concluded that 75% of children who read nine or more books a month read above the level expected of them, compared with 28.6% of those who read no books in a month.
Trust director Jonathan Douglas said the numbers of children without books were of "particular concern".
"We know there is a direct correlation between book ownership and children's reading abilities," he said. "With one in six in the UK struggling with literacy it is very worrying that many children could be missing out on opportunities to develop these essential skills."
The survey was commissioned to mark the launch of the Trust's Christmas Gift of Reading fundraising appeal.