Fewer mothers are breastfeeding in Scotland despite years of initiatives to encourage the practice, with latest figures showing the lowest take-up for six years.

In some areas, fewer than one in five newborn babies are purely breastfed and the rate for the country is little more than one in four.

Advertising campaigns, government targets and a change in the law enshrining the right to breastfeed in public appear to have made little difference.

Data shows there was sign of slight improvement in 2005, but rates have now dipped back to those recorded at the start of the millennium.

NHS Health Scotland is to commission research to probe the roots of the problem.

Ann Kerr, team head for early years, food and active living at the NHS Health promotion agency, said: "There are a huge number of benefits to breastfeeding. It helps protect the baby against infection. They acquire the mother's immunity to common viral illnesses and also appear to be protected, to a certain extent, from allergies such as asthma and eczema and type one diabetes."

Research has also shown breastfed infants are less likely to become obese. A new study, published today, suggested women could cut their chance of developing rheumatoid arthritis by as much as half by breastfeeding and it also thought to help women avoid some types of cancer.

The World Health Organisation recommends children are exclusively breastfed until they are six months old.

However, in Scotland in 2007 the proportion of infants just drinking breast milk at six to eight weeks was 26.4%. This compares to 28.1% in 2005 and 26.7% in 2001.

Mrs Kerr said although legislation guaranteeing women the right to breastfeed in public came into force in 2005, the culture had not yet changed.

"People do not feel comfortable yet," she said.

This and other factors were flagged-up by a review of research on what influences mothers' decision-making.

Mrs Kerr said: "One of the other things which came out was around body image and self-esteem. How confident women feel about themselves and their bodies may be important."

In some parts of Scotland breastfeeding is much less common than others. Compliance with the guidance at the stage of six to eight weeks varied from 35% in NHS Lothian to 18.8% in NHS Ayrshire and Arran. Fewer women adopt the practice in deprived areas, with rates as low as 13.9% in the poorest communities and as high as 42.3% in the most affluent.

However statisticians also said the gap had narrowed slightly in recent years.

Scotland has already missed a government target to have 50% of mothers breastfeeding by 2005. The new goal, set last year, is to increase the proportion of newborn children exclusively breastfed at six to eight weeks to 32.7% in 2010.

A Scottish Government spokeswoman: "We have recruited an infant nutrition co-ordinator for Scotland, who will work on the development of an infant nutrition strategy for Scotland.

"Part of this work will focus on the promotion of breastfeeding as key to ensuring optimal nutrition for infants."

Elaine Smith, the MSP who led the drive to give women the right to breastfeed in public, said: "I am pleased to see that the rates of breastfeeding have increased in the most deprived areas. These statistics indicate that a small but significant attitudinal shift is occurring amongst mothers."