A Labour government will impose VAT on private school fees to pay for free meals for all primary school pupils, Jeremy Corbyn is to announce.
The Labour leader will say on Thursday the policy will boost the health and educational attainment of all children while ending a "subsidy to the privileged few".
The announcement will be seen as an attempt to regain the political initiative following rows over the party's poor showing in the opinion polls and allegations of anti-Semitism against Ken Livingstone.
Mr Corbyn will point to research showing that offering universal access to free school meals improves pupils' productivity, enabling primary school pupils to advance by around two months on average.
"No child in the UK should go hungry at school. By charging VAT on private school fees, Labour will make sure all primary school children, no matter what their background, get a healthy meal at school," he will say at a launch event in Lancashire.
"The next Labour government will provide all primary school children with a free school meal, invest in our schools, and make sure no child is held back because of their background."
Labour will say the provision of free school meals also improves the health of pupils through better nutrition - with over 90% of pupils who have a school lunch consuming food or drink containing vegetables or fruit compared with just 58%
Shadow education secretary Angela Rayner will say Government cuts to school budgets were leading to a deterioration in the quality of school meals while limiting the numbers of pupils who can receive them.
"While the Conservatives offer tax giveaways to their billionaire friends, they are cutting the schools budget and threatening the health and futures of all our children by denying children the basic right of a healthy lunch at school," she will say.
"By investing in our education system and providing free school meals for every primary school child, we will remove the stigma attached to free school meals, and improve health and attainment for all children."
Children in reception year 1 and year 2 already get free school meals and Labour said that extending the scheme to all primary school pupils had been estimated to cost between £700 to £900 million a year.
The party said that an estimate by the Fabian Society in 2010 suggested that introducing VAT on private school fees could raise around £1.5 billion annually.
However a Conservative spokesman dismissed the plan saying: "Labour would wreck the economy if they ever got back into government - meaning there would be less money to spend on our schools, not more.
"Their economic incompetence means this promise isn't worth the paper it's written on."
The Independent Schools Council (ISC), representing private schools, said Labour's proposals did not add up and would force some smaller schools to close.
"A third of pupils at our schools are on reduced fees and are from families where both parents work hard to pay the fees," said ISC general secretary Julie Robinson.
"If this measure was introduced smaller independent schools may close, driving more children back to be funded in the state system. 600,000 children are educated in independent schools, saving the taxpayer the cost of educating them.
"Independent schools are fully aware of their social responsibilities and offer free and reduced cost places to children from lower income homes.
"They also partner with state schools to offer support with sciences and languages, A-levels and university access, as well as sport and music."