One in five children finishing primary school in Lancashire are obese.
Campaign group the Obesity Health Alliance says children are surrounded by unhealthy food and drinks, and is calling for bold government action to prevent further harm.
NHS Digital data shows that 20 per cent of Year 6 pupils in Lancashire in 2018-19 were obese.
This was up on the 13 per cent considered obese in 2006-07, the earliest year with available data.
Additionally, 15 per cent of Year 6 children were overweight last year, just higher than 13 per cent in 2006-07.
That means 34 per cent of the area’s pupils in the last year of primary school were unhealthily overweight.
And four per cent were severely obese, with a BMI in the top one-in-250 for children.
Across England, four per cent of 10 and 11-year-olds were classed as severely obese in 2018-19, a record high for the fourth consecutive year.
The obesity rate, which includes severe obesity, also hit a record high of 20 per cent, while the figure rises to 34 per cent when overweight children are included.
Caroline Cerny, of the Obesity Health Alliance, a coalition of organisations working to reduce obesity, said children are growing up in an environment that is “flooded” with unhealthy food and drinks, which are damaging their health.
She added: “It’s time for the Government to bring in the measures that we know will stem the tide of unhealthy food marketing and promotions, starting with the long overdue 9pm watershed on junk food adverts on TV and online.”
Public Health England works out obesity using the 1990 British growth reference chart, a large collection of statistics used to determine a child’s BMI. It defines a child as obese if their BMI is in the chart’s top five per cent and overweight if they are in the top 15 per cent.
Obesity can lead to heart problems and type 2 diabetes later in life, as well as psychological issues such as low self-esteem and depression.
The data also suggests that children often develop weight problems while at primary school.
In 2018-19, just 10 per cent of Lancashire’s children were obese in Reception.
Across England, Year 6 children from the most deprived backgrounds were more than twice as likely to be obese than those from the wealthiest areas.
NHS chief executive Simon Stevens said obesity is a “dangerous public health threat” for children, and that the figures show the country is not on track to meet the Government’s goal of halving childhood obesity.
“While the NHS will be there for patients, services and budgets will obviously be placed under more strain,” he added.
“So we also need combined action from parents, businesses and government to safeguard our children from this preventable harm.”
Public health minister Jo Churchill said: “This problem has been decades in the making but we can turn this around.
“Our world-leading childhood obesity plan will help all families by making the healthiest choice the easiest choice, whether at home, at school, or at play.
“We are working with councils to tackle child obesity locally through new and ground-breaking programmes, cutting large amounts of sugar from food and soft drinks, and investing millions to give children opportunities to exercise in schools.”