The figures published for the first time show that 40 per cent of pupils - almost 240,000 - fail to achieve the expected standard in reading after a year of school.
The data from Department for Education, based on a new controversial test, revealed that boys in UK are already slipping far behind girls in terms of their ability to accurately decode a list of 40 words.
The report said that white British boys from the poorest backgrounds officially performed worse than any group, 'The Telegraph' reported.
As many as 37 per cent of these children reached the standard expected of their age group.
The findings raise concerns that some groups of children - particularly boys - failed in the early years.
Experts claim that a lack of male role models at home and school may be turning boys off reading at a young age.
However, the government insisted that the new assessment would enable schools to pick out pupils falling behind at the start of compulsory education.
"The reading check helps teachers identify those pupils who need extra help in learning to read. Many thousands of children will now receive the extra support they need to develop a love of reading," Elizabeth Truss, the Education Minister, said.
