A report ordered by the Government could see a further 1.5 million children benefitting from free school meals, as well as provisions for poorer children during the school holidays.

Currently only children from households earning less than £7,400 before benefits are eligible for the scheme, but The National Food Strategy, led by Leon restaurant founder Henry Dimbleby, is calling for change.

It warns that poorer children are at rick of being "left behind" after the coronavirus pandemic.

The report said: "One of the miserable legacies of Covid-19 is likely to be a dramatic increase in unemployment and poverty, and therefore hunger.

"The effects of hunger on young bodies (and minds) are serious and long-lasting, and exacerbate social inequalities."

The study proposes an expansion of free school meals to every child where a parent is receiving Universal Credit.

Expanding the programme could reach an additional 1.5 million seven to 16-year-olds at a cost of £670 million a year.

The report also calls for an expansion of the holiday activity and food programme to all areas in England, reaching an extra 1.1 million children at a cost of £200 million a year.

It also urges an increase in the value of Healthy Start vouchers to £4.25 per week and expansion of the scheme to pregnant woman and households in receipt of Universal Credit with children under four.

The vouchers can be spent on vitamins, fruit, vegetables and milk, and the recommendation would mean an extra 290,000 pregnant women and under-fours would benefit, the study said.

Mr Dimbleby said the chief executives of Waitrose and the Co-Op have already agreed to supplement the vouchers with extra free fruit and vegetables.

He welcomed the Government’s obesity strategy, released on Monday, but said some firms need to look at their actions when it comes to creating foods that appeal to children.

Mr Dimbleby attacked Marks & Spencer over its Percy Pig sweets, saying they are marketed on the front as containing all natural fruit juice and are placed "right by your kids’ little fingers".

And yet, he said, the first four ingredients listed are forms of sugar such as fructose syrup and glucose-fructose syrup.

He said: "And actually, when you look at the food world, the reason I pick M&S is because they have integrity as one of their values, but it is rampant in the food world – you know, low fat (food) which is actually high in sugar, or free from this and that.

"I think CEOs do have to respond to commercial pressures but they are not innocent, bobbing about on the waters of commerce, unable to take any value-based decisions.

"I think they do need to take a look at what they’re doing. I think boards in these companies very quickly, if they were to ask these questions, could, without any need for regulation from Government, improve the system a lot.

"I think it’s time they realised that they have been putting their head in the sand for too long."

He hinted that taxes could be used to tackle fattening and sugary foods, however he disagreed with calls for plain packaging of sweets,

Mr Dimbleby, who said he struggles with his own weight, said he agreed that some fruit snacks are "being clothed in a veneer of goodness and might not be better for you than a Mars bar".

He urged the Government to implement the recommendations in the report quickly.

"In doing so, it will improve the health of the nation and be a necessary pillar of its ambition to level up society," he said.

Susan Jebb, professor of diet and population health from the University of Oxford, who worked on the report, said: "A nutritionally poor-quality diet is the leading risk factor for ill-health in the UK, yet we do not treat it with the same seriousness afforded to other risk factors. That has to change.

"The Covid-19 pandemic has been a wake-up call that obesity in particular increases the risk of suffering serious complications from the virus, but a poor diet also increases the risk of diabetes, heart disease and some cancers.

"This report makes clear the gravity of the situation and the stark inequalities that are evident across the food system."

Environment Secretary George Eustice said the entire food supply chain had "worked around the clock" during the pandemic, while "Government has invested record levels to support the most vulnerable in our society".

He said: "But we know there is more to do, and we will carefully consider this independent report and its recommendations as we emerge from the pandemic and build a stronger food system for the future."