Next is offering plus-size clothes for children as young as three which some health experts suggest is a sign of the UK's growing problem with childhood obesity.
The "plus fit" range for boys and girls consists of over 40 items designed for children with larger waistbands.
The fashion chain is thought to be the only major clothing store in Britain to be selling casual wear children with larger-than-average waists, according to the Telegraph.
The retailer's "age 3 plus fit" trousers have a waistband which is 5cm larger than a standard "age 3" waistband, at 58 cm compared to 53 cm, the newspaper reported.
Next's "Age 10 plus fit" trousers are also said to have a waistband of 69 cm, compared to a 64 cm measure on standard "age 10" trousers.
Tam Fry, chief executive of the National Obesity Forum, told the Telegraph: "Next is simply catering for the market and the size of existing market is getting bigger, so they will be putting up their sizes. They may get stick for it but they are simply saying we have to clothe our customers.
"They are responding to current state of affairs, It has been in a bad state for a long time but this just shows it has now gone beyond the point of a crisis.
He added: "The UK is sitting on a time bomb of childhood obesity, children are several times fatter than they were in 2002."
A spokesman for the fashion retailer told ITV News the ‘plus-fit' range, which includes school as well as casual wear, was first introduced in 2007.
In 2010, Marks and Spencer trialed a plus size range of children's clothes for child as young as three but decided not to make it permanent.
The retailer currently offers a limited plus range for children from the age of four.