Pregnant women who eat large amounts of chips and crisps could be harming their babies as much as smokers, a new European study suggests.
Women and babies from England, Denmark, Greece, Norway and Spain were tested for levels of a potentially toxic chemical found in fried potatoes.
It found babies from Bradford, who represented England, had the highest levels and lower birth weights.
The study was led by the Centre for Research in Environmental Epidemiology.
Researchers found infants born to women with a high dietary intake of the chemical, called acrylamide, were found to be 132g (4.6oz) lighter than babies born to mothers who had a low intake.
They also found the infants' heads were up to 0.33cm smaller.
Tracking the health
Researchers said the size of a child's head has been associated with delayed neurodevelopment, while lower birth weights have been associated with adverse health effects in early life and as children grow up.
The study, led by the Barcelona-based centre, is claimed to be the first in humans to examine the association between acrylamide exposure during pregnancy and birth outcomes.
Prof John Wright, from the Bradford Institute for Health Research, said: "The effect of acrylamide is comparable with the well-known adverse effect of smoking on birth weight."
The study looked at the diet of 1,100 pregnant women and newborns from the five European countries.
The babies taken to represent England were drawn from the Born in Bradford project, which is tracking the health of more than 13,500 babies from womb to adulthood.
Dr Laura Hardie, from the University of Leeds, said: "One hundred and eighty six women from the Born in Bradford study took part in this major European research programme.
"We found that their babies had the highest levels of acrylamide out of all the five centres - almost twice the level of the Danish babies.
"When we investigated their diet it was clear that the largest source of dietary acrylamide is from chips."
Prof Wright said women's diet in Bradford was similar to the rest of the UK, which consumes several billion packets of crisps a year.
"The UK tends to have high levels of acrylamide in the diet and this is a reflection of the type of diet that we have."