Marks & Spencer has launched a range of school clothes for fat children as young as four. The Plus range offers waistlines up to 41 inches. The retailer said it is merely meeting a demand by parents.
“We want to make sure our schoolwear range is accessible for children of all shapes and sizes,” said a company spokesperson.

Tam Fry, of the National Obesity Forum, said, "This is the actual commercial recognition of what we have known for some time - that obesity in pre-schoolers is building up. Now 27% of entrants to primary schools are overweight or obese."

Mr Fry said there needed to be a collective effort to curb obesity. "Parents should not fail in their responsibility - it is they that put food in their children's mouths, send their children out to play. But at a government level, they have consistently ducked out of regulating the food industry.

"If you allow the food industry to self regulate - and the government sanctions the fact that they are not going to regulate - then the food industry will just carry on making the food it is making."

A spokesman for Marks and Spencer said, "It is a small online trial running in response to customer demand. Marks and Spencer is the leading schoolwear retailer and we want to make sure our schoolwear range is accessible for children of all shapes and sizes."

Obesity costs the NHS more than £4 billion a year and is set to soar to £6.3 billion a year by 2015. By 2050 the burden of the problem is expected to cost an incredible £50 billion a year.

According to the British Medical Association, about a quarter of boys and a third of girls aged between two and 19 are overweight.

A M&S spokesman said the new uniform range had been introduced "quietly" and without advertising.

"We are the market leader in school ­uniforms and we want to make sure we provide for everyone. We did an advertising campaign for schoolwear but not Plus schoolwear because it is a low-key trial. But the demand from parents has been significant."