Forty per cent of children struggle to write their own name or to sound out letters to form simple words such as “dog” or “red” by the age of 5, government figures show.

The annual assessments of children’s progress during their first year in school also show that more than a fifth of youngsters have problems stringing a coherent sentence together by the time that they enter their reception year.

A quarter fail to reach the expected levels of emotional development for their age.

The findings raise serious questions about the effectiveness of flagship government schemes such as Sure Start to boost the development of the under-5s, although some critics point out that in many countries children are not expected to start to read or write until they are 7.

Around £21 billion has been invested in a series of initiatives but the latest results for schools in England show little improvement in children’s language and literacy and personal, social and emotional development.

Sure Start was also supposed to help to narrow the attainment gap between children from poor backgrounds and the rest, but only 35 per cent of children from poor areas reached the expected level of attainment across all measures, compared with 51 per cent of children from other areas.

The achievement gap has not moved since last year and the overall levels of achievement, at 45 per cent, are well short of the target of 53 per cent by next year.

David Laws, the Liberal Democrat spokesman for children and families, said that the “yawning gulf” between rich and poor was deeply disturbing.

Maria Miller, the Conservative families spokeswoman, said that the data, released by the Office for National Statistics, showed that Sure Start was not working.

Beverley Hughes, the Children and Families Minister, conceded that more improvement was needed. She was disappointed that the gap between poor and middle-class children had not narrowed.

She added: “Both we and local authorities must focus our efforts on improving the life chances of children who are the most vulnerable and disadvantaged.”

The foundation profile targets require five-year-olds to score at least six out of nine points in each of seven areas of learning covering language and literacy and personal, social and emotional development.

Girls outstripped boys in every one of them – by 17 percentage points in the case of writing.

Only 58 per cent of five-year-olds were reaching a “good level of development” in writing. One in three children (35 per cent) did not reach a good level of development in linking sounds and letters, for example through recognising and saying words such as “red” and “dog” or “pen”.

Fifteen per cent could not write “mum”, “dad” or their own first name from memory, while a further 25 per cent struggled to do so.

But the assessments, which are known as the Foundation Stage Profile, were criticised by teaching unions last night. Mick Brookes, the general secretary of the National Association of Head Teachers, called them “unreliable and unhelpful” because they are based on subjective teacher observations, not tests.

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