Findings of a cot death study that helped to discredit the paediatrician Professor Sir Roy Meadow were challenged by a report published yesterday in the British Medical Journal.

A paper published in 2005 in the medical journal, The Lancet, suggested that the vast majority of second infant deaths in families who have already lost a baby were due to natural causes. In 2005, research led by Prof Robert Carpenter, of the London School of Hygiene and Tropical Medicine, found that as many as 90 percent of second deaths were natural.

The study was based on more than 6,000 babies who passed through the Care of the Next Infant (Coni) scheme, set up by the Foundation for the Study of Infant Death.The paper was published when murder convictions connected to sudden infant deaths were being reviewed. The BMJ report, led by investigative journalist Jonathan Gornall, alleges that classification of deaths in the study were changed after the death of a senior researcher, Professor John Emery, who had prepared a report on the Coni scheme in 1998 and concluded that 40 per cent were "unnatural". But, by 2005, the proportion of "unnatural" deaths had fallen to 13 per cent, because some had been re-categorised as natural. Others were excluded and 13 unclear deaths were listed as "natural". The BMJ report says: "The authors created the illogical corollary that all the deaths in the series that were not unnatural must be natural."