Free school meals should be extended to 1.5 million more children and those less well off should be fed in the school holidays, a Government ordered review found.
Leon restaurant founder Henry Dimbleby warned poorer children risk being “left behind” and demanded action to avoid a “slow-motion disaster”.
He delivered the National Food Strategy amid fears thousands of children will go hungry after the coronavirus pandemic.
Mr Dimbleby 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.”
It comes as it emerged Boris Johnson’s junk food advertising watershed of 9pm will take two years to be introduced.
Despite health campaigners saying the ban is “long overdue” ministers will give food firms the time to make food healthy enough to promote.
The study proposes an expansion of free school meals to every child where a parent is receiving Universal Credit.
At present, only children from households earning less than £7,400 before benefits are eligible.
Mr Dimbleby added: “Children who are hungry at school struggle to concentrate, perform poorly, and have worse attendance records.”
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.
And it 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.
Prof Susan Jebb, of Oxford University, 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.”
Part Two of the National Food Strategy is due to be published next year and will look at issues including climate change, pollution and antimicrobial resistance.
