CHILDREN whose mothers return to full-time work before they are 18 months old are slower to develop basic learning skills, according to a study published today.

The report on working mothers in the UK said 14pc of mothers go back to full-time work within the first year and a half of their child's life.

It found the reading, writing and speaking of these children, between the ages of two and eight, were "negatively affected."

The study also found there were "significant ill-effects" on the development of children who were cared for by a friend, relative or neighbour while their mother worked full-time.

A team from Bristol University assessed the development of more than 12,000 children born in 1991 and 1992 at four stages and compared the findings with their mothers' working patterns.

The tests were part of the Children Of The 90s project, which has been monitoring 14,000 children in Bristol since 1991.

The report read: "There are negative effects only for the relatively unusual group of children whose mothers return to full-time work before they are 18 months old. The magnitude of these effects is small, and only 14pc of mothers do go back to full-time work this early.

"It is only those children whose non-parental care consists solely of unpaid care by a friend, relative or neighbour who experience significant detrimental effects.

"Short periods of care by relatives appear not to be damaging: it is sole reliance on relatives to cover full time working that appears to be less beneficial."

The researchers also found maternal employment in the first three years of life appeared to have no adverse effect on later cognitive outcomes.

Report authors Paul Gregg and Liz Washbrook said it was important to realise the need for inexpensive and high quality child care for very young children. They said: "Relatively few mothers in our study made use of paid care before their children reached the age of two, probably due to the prohibitive costs.

"The recent increases in financial support for child care may lead to a shift towards paid care."

The Department for Education and Skills funded the work.