Labour would impose VAT on private school fees to pay for free meals for all primary school pupils.
The policy would boost the health and educational children across the board while ending a "subsidy to the privileged few", the party claim.
Labour leader Jeremy Corbyn is set to announce the policy on Thursday while hoping to divert attention from the party's poor opinion poll showing and an anti-Semitism row against Ken Livingstone.
Mr Corbyn will draw on research showing that access to free school meals improves pupils' productivity.
"No child in the UK should go hungry at school," Mr Corbyn will say at the event in Lancashire.
"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.
"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 cite research which claims free school meals improve the health of pupils by being a better source of nutrition.
Currently only 58% of primary school pupils have a school lunch containing fruit or vegetables, but Labour hope to increase this to 90%.
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.