Children become obese because of the influence of their same-sex parent, not as a result of genetics, a new study by British scientists claims.

Scientists from Peninsula Medical School at the Universities of Exeter and Plymouth say if a young girl has an overweight mother she is more likely to become obese, with the same applying to boys and their fathers.

The findings suggest that it is behavioural rather than genetic factors that have a greater influence in determining whether children become obese.

According to the study of 226 British families, the scientists found that obese mums were 10 times more likely to have obese daughters.

Obese dads were also six times more likely to have an obese son.

However, the same trend did not exist between mums and their sons and fathers and daughters.

"Any genetic link between obese parents and their children would be indiscriminate of gender," the study's director Professor Terry Wilkin said.

"The clearly defined gender-assortative pattern which our research has uncovered is an exciting one because it points towards behavioural factors at work in childhood obesity."

Prof Wilkin said the findings could dramatically affect government policies on dealing with childhood obesity and its current focus on an apparent genetic link.

"Money and resources have focused on children over the past decade in the belief that obese children become obese adults and that prevention of obesity in children will solve the problem in adulthood," he said.

"(The study's) evidence supports the opposite hypothesis - that children are becoming obese due to the influence of their same-sex parents and that we will need to focus on changing the behaviour of the adult if we want to combat obesity in the child."