Supermarkets want laws to force a 50 per cent cut in the sugar content of cakes, biscuits, breakfast cereals, chocolate bars, sweets and fizzy drinks.

The measure would compel retailers, fast food chains, coffee shops and others to reduce sugar – in the biggest change in the national diet ever seen.

It is a remarkable U-turn for supermarkets – which have previously fought legal controls on sugar content – and means they have effectively joined forces with health campaigners.

Supermarkets are backing proposals to cut the sugar levels in sweets by 50 per cent (file picture)

The law would require a radical change to the recipe of popular foods and some may have to cut portion sizes.

Food groups included in the crackdown would be biscuits, cakes, pastries, fruit pies and puddings. Also on the list are sweets, chocolate bars, yogurt, dairy desserts, breakfast cereals, sugar-sweetened drinks and even table sugar.

Manufacturers might reduce sugar in stages, on the basis consumers would get used to the taste over time.

Alternatively, sugar could be replaced with lower-calorie natural alternatives, such as plant extract stevia.

Supermarkets want mandatory controls, requiring sugar to be removed from foods, to be the centrepiece of the Government’s childhood obesity strategy, expected in February.

In the past the retail giants supported measures under ‘Responsibility Deals’ set up by the Government to ask firms to make reductions voluntarily.

But the British Retail Consortium, which speaks for supermarkets, said these have failed to deliver the comprehensive sugar cuts necessary to protect the nation’s health.

The Government has also given up on the deals, with ministers apparently willing to adopt tougher legal controls.

The BRC’s Andrew Opie said: ‘We believe we’ll make the most progress by having targets for reducing sugar from those categories contributing the most to excessive consumption by children, as part of a wider reduction strategy.

‘To be effective, they need to apply to all food companies, which is why they need to be mandatory … It means we see change across the board and those companies that are more progressive in removing sugar are not penalised.

Experts say the sugar reductions could reduce the amount of sugar consumed by children by 26g per day, or around 6.5 teaspoons (file picture)

‘We recognise that reducing sugar is not the only approach and in some cases we would look at other methods such as appropriate portion sizes alongside targets.

‘We believe this approach is possible through consultation to agree appropriate targets and reduction over a suitable period that allows consumer tastes to change and companies to adapt.’ The proposals echo a recent Public Health England study, Sugar Reduction: The Evidence for Action.

The PHE estimated that cutting the sugar content of targeted foods by 50 per cent would reduce the amount consumed by children aged 11-18 by 26g a day – 6.5 teaspoons.

Sugar consumption for those aged four to ten would fall by 19g a day and the figure for adults by around 17g a day.

Health experts argue this would be sufficient to halt the growing obesity epidemic that is fuelling ill-health, including heart disease, type 2 diabetes and some cancers.

The study also raised the possibility of adding a sugar tax to fizzy drinks, but David Cameron is understood to be opposed to this. Professor Graham MacGregor, of campaign group Action on Sugar, described the supermarkets’ support as ‘an amazing breakthrough’.

But there is opposition from some manufacturers, restaurants and food chains.

Tim Rycroft, of the Food & Drink Federation, said firms should be able to decide for themselves how to deal with sugar rather than being forced to make changes.