The government's efforts to improve early-years education have not had a significant effect on children starting primary school, research has found.
Academics at Durham University looked at the impact of the government's various pre-school initiatives on school starters, using performance indicators in primary schools (PIP).
Researchers at the university's Curriculum, Evaluation and Management Centre looked at the cognitive abilities of five-year-olds as they entered school between 2001 and 2006.
They found little tangible evidence that the measures, ranging from Sure Start to the Children's Act, had improved the development and skills of young children.
Researcher Dr Christine Merrell said: "One would have expected that the major government programmes would have resulted in some measurable changes in our sample of almost 35,000 children.
"It is possible, however, that it is just still too early to measure the effects of these programmes, particularly those of the Children's Act and Every Child Matters, which were only introduced in the past few years."
The government maintains early years education is having an effect, as is reinforced by other studies.
Children's minister Beverley Hughes said: "The government has invested over £21 billion on early years and childcare services since 1997 as part of an unprecedented expansion of provision for young children and families.
"Early indications are that this investment is improving outcomes for children.
"However, as the author of this report acknowledges, it is still too early to measure this with any great authority."
The Conservatives, however, said the government had introduced a volley of initiatives without stopping to review their effects.
Shadow schools minister Nick Gibb said: "We need a scientific approach to education and more needs to be done to ensure the curriculum in early years in particular helps children from poorer backgrounds be ready for school in their reception year".
The government has introduced a range of measures to target children's skills before they enter school, including the Sure Start programme, free nursery education for all three-year olds, the Children's Act 2002 and Every Child Matters programme.