More than a third of the poorest children do not have the internet at home and a similar number do not have a computer, official figures suggest.
A new breakdown of Office of National Statistics (ONS) data also showed that children from the wealthiest homes all had internet and computer access.
Campaigners say this 'digital divide' can harm poor pupils' education.
Valerie Thompson of the E-Learning Foundation says children without home internet "lose out big time".
She said, at the most basic level, lack of a home internet connection or a computer could mean that children struggled to research homework or complete coursework and were unable to access school websites which allow pupils to submit work digitally and receive feedback from teachers.
"These new statistics show the digital divide is still a major issue for this country's young people.
"Poverty is clearly a factor in poor access to digital learning technologies and poor performance at school. The link between the two cannot be ignored."
The latest ONS Family Spending Survey, published last month, analysed the income and expenditure of more than 11,000 households across the UK. The data was collected in 2011.
The charity, E-Learning Foundation, extracted the data on computer ownership and internet access for families with children aged under 18.
Overall, most children (89%) can get on to the internet via a computer at home but according to E-Learning Foundation this figure masks a divide between rich and poor.
The data shows that while 99% of children in the richest 10% of households can access the internet via a computer, this dropped to 57% in the poorest 10% of households with children.
In the poorest households 29% had no computer, 36% had no internet and 43% had no internet connection via a computer.
According to the E-Learning Foundation this translates to a total of 750,000 school age children living in households with no internet, and some 650,000 without a computer.
'Teenagers and Technology'
A book from Oxford University's Department of Education, published this month, highlights the ways in which teenagers without an internet connection feel shut out from their peer group and disadvantaged in their studies.
The authors of Teenagers and Technology also found that parental fears about teenage time-wasting on social network sites were often unfounded with the benefits using digital technologies outweighing perceived risks.
A 15-year-old interviewed for the book commented "It was bell gone and I have a lot things that I could write and I was angry that I haven't got a computer because I might finish it at home when I've got lots of time to do it."
And a 14-year-old boy talked about how much harder it was to complete coursework without a home computer: "People with internet can get higher marks because they can research on the internet."
He added that he felt cut off from friends because of being unable to access social networks: "My friends are probably on it all day every day and they talk about it at school".
Co-author Rebecca Eynon said: "Behind the statistics, our qualitative research shows these disconnected young people are clearly missing out both educationally and socially."
E-Learning's Valerie Thompson said imaginative use of technology by schools could help overcome the educational disadvantages suffered by children on free school meals, a key indicator of poverty.
"Technology can underpin learning by making it more relevant and personalised," she said.
"It can also help children with special educational needs, particularly those who struggle to cope in a normal, classroom, helping them learn and complete work at their own pace.
"Technology can allow a school to deliver an education to a child wherever they are, not just in a classroom."
She called for the social housing providers such as housing associations and local authorities to install wi-fi connections for tenants, and for schools to use the government's pupil premium for disadvantaged pupils to buy laptops for the poorest.