Three-year-olds should be made to walk on short trips out rather than being strapped into buggies, the public health minister has urged.
Nationally almost one in five 10 and 11-year-olds are obese, and the problem frequently starts before school age.
Politicians yesterday said parents should take responsibility for their children's weight and fitness, with Anne Milton, the public health minister, saying: "Encouraging children to walk is one way of getting the whole family to take more exercise."
She was speaking after Nickie Aiken, Westminster Council's cabinet member for children, and a fellow Conservative, told a newspaper that parents who relied too much on the buggy to ferry their young children from A to B risked damaging their charges' long-term health.
She said: "We have to acknowledge childhood obesity is a growing problem.
"While local authorities have a part to play it is ultimately the responsibility of parents and carers.
"By taking steps such as encouraging children to walk to school, to eat healthily, or stop using buggies on short trips at the age of three, they can help ensure their children lead an active life."
Ms Aiken, who has two children aged five and seven, emphasised she understood that it was not always easy for time-pressured parents to afford the luxury of letting small children dictate the pace on the way to the shops.
Mothers or fathers who had to get their older children to school on time might feel the need to hurry things along by putting a smaller child in a buggy, for example.
But she said: "I get very frustrated when I see children as old as five in a buggy. We should start to stop using the buggy as much as we can from three."
The use of buggies to transport children aged three and over does appear to be a growing trend, helped by the advent of larger and stronger buggies on the market.
Ms Aiken is particularly concerned because Westminster borough has one of the highest rates of childhood obesity in the country, with almost a third of 10 and 11-year-olds classed as obese.
Mrs Milton, a former nurse, is the MP for Guildford, one of the most affluent constituencies in the country. She has four children.
Last year she suggested that doctors should tell seriously overweight people that they were simply fat, as she believed the word had more impact than 'obese'
Children from poorer backgrounds are more likely to be fatter than those from better-off homes. However, children of all social classes are bigger now than they were a generation ago.
While studies show that the most important single factor is that children eat more now than they did in the 1980s, declining levels of activity are part of the problem too.
In July the Government published new guidance recommending that under-fives should get three hours' exercise per day, such as free play or walking. However, only a third get enough.