A fifth of all children in the region who have free school meals fail to reach the accepted standard for reading, writing and arithmetic, according to charity Save the Children.
Children who are behind in the "three Rs" at the age of seven already have their life chances virtually determined, the charity says.
In a new report, "Too Young to Fail," Save the Children said being behind at these core subjects at such a young age could prejudice a child's future earnings, health and, in economic terms, cost the country billions in lost revenue.
Shocking figures have revealed that Yorkshire has one of the highest rates of child poverty in the country. The rest of the region fares little better, with tens of thousands of youngsters missing out on basic essentials - warm clothing, shoes, and even food.
The figures have been released today by the charity Save the Children, which is now turning its attention to poverty-stricken Britain for the first time ever, blaming the Government's austerity measures.
The Government has responded to a report by Save the Children, which has found that a third of children in Yorkshire and the Humber and a quarter of children in the East Midlands, which includes Lincolnshire.
A spokesperson said: "Despite £150bn being poured into benefits and tax credits over the last decade, the previous Government's approach to tackling child poverty has failed with the UK missing its own 2010 child poverty targets.
We have spoken to Graham Whitham from Save the Children, who has written a report outlining that a third of children in Yorkshire and the Humber and a quarter in the East Midlands, which includes Lincolnshire, are in living in poverty.