From wires reports - Children who do not reach key developmental milestones at just nine months old are far more likely to struggle at school, according to an important study published last week.

The United Kingdom’s Millennium Cohort Study of nearly 15,000 children says that babies who were slow to develop their motor skills at nine months were significantly more likely to be identified as behind in their cognitive development, and also likely to be less well behaved at age five.

The findings will intensify the debate on how far the government should intervene to stop those from disadvantaged backgrounds falling behind before they even reach school. The correlation between performance at nine months and five years was said to be significant even after the researchers considered the impact of poverty on children's development.

The difficulties facing children from poor backgrounds are likely to be a key election battleground.

Early last week, a study by the Sutton Trust charity found that children from the poorest homes are more than a year behind their peers from well-off backgrounds in their acquisition of vocabulary by the time they start school.

However, critics of early intervention say parents should be left to bring up their children without detailed monitoring.

Academics from London University's Institute of Education analysed the progress of 14,853 children, born in 2000 and 2001, from birth to five. The children's cognitive development was assessed at the age of five through a series of vocabulary, spatial reasoning and picture tests, and their results compared with those from separate assessments years earlier.

The results at five were strongly linked to the babies' abilities in tests for gross motor development, such as crawling, and fine motor development, such as holding objects with their fingers, at nine months. The researchers also found that children who are read to every day at three are likely to be flourishing in a wide range of subjects by the age of five.

Children who failed at nine months to reach four key milestones in gross motor development, relating to sitting unaided, crawling, standing and taking their first walking steps, were found to be five points behind on average in cognitive ability tests taken at age five, compared to those who passed the milestones. This equates to the difference between being in the middle of the ability range in the cognitive tests, and being below average.

Ingrid Schoon, professor of human development and social policy at the institute, who led the research, said: "Delay in gross and fine motor development in a child's first year, which affects one in 10 children, was significantly associated with delayed cognitive development at age five. Delay in gross motor development also has a significant impact on the child's behavioural adjustment at five."

The report said: "This finding highlights the importance of early screening for developmental delay at ages under one year, as a tool to promote positive child development."

Any move to intervene so early in a child's life by providing extra support for some babies from nine months would be controversial. In 2006, Tony Blair faced criticism after claiming that troublemaking children of the future could be identified before they were born, by targeting families with, for example, drug and alcohol problems. Identified families could then be forced to take help.

Sue Palmer, the author of Toxic Childhood, said: "We would do better to empower parents with more information about what they can do to help their babies, rather than professionalising the whole basis of childhood, which is what you do when you intervene early."

Professor Peter Tymms, director of Durham University's centre for evaluation and monitoring, said the study's findings fitted a pattern of children's school achievements being predicted by their performance in tests of understanding from an early age, but it was unusual to have found statistics predicting future cognitive difficulties before the age of one. He added: "There should be more evidence before we go for a nationwide intervention such as screening tests. There are pluses and minuses of interventions: we might be able to help some children, but screening could also cause anxiety to children and their parents identified as needing help."

The Department of Health said: "Children's health and wellbeing is a key priority for [the] government. The department looks at a range of research and will consider this report alongside all others.

"The Healthy Child Programme for the first years, relaunched in October 2009, focuses on a universal preventative service, providing families with a programme of screening, immunisation, health and development reviews."