Free school meals will be available to all primary school children in England, under a £610m-a-year plan unveiled by the Liberal Democrats.
Infant school pupils are already entitled to a free meal under a policy championed by leader Nick Clegg and introduced in September last year.
But Mr Clegg wants seven to 11-year-olds to also benefit from 2017/18.
The Lib Dem pledge came as the Tories promised not to raise taxes and Labour said it would ensure tax credits rise.
Mr Clegg and his wife Miriam, who runs a food blog, donned aprons and made an apple and blackberry crumble for pupils at a Wiltshire school to promote the measure, which they claim will benefit 1.9 million youngsters and save parents £400 per child on lunches.
Mr Clegg said his policy would also ensure all primary school children enjoyed a nutritious meal rather than a “slice of white bread with chocolate paste on it”.
The introduction of free school meals for Key Stage 1 pupils faced criticism over the way it was funded, with some councils raiding maintenance budgets to meet the obligation.
Under the expanded Lib Dem plan, an estimated £100m would be earmarked for improvements to school kitchens and dining facilities in primary schools.
The extension of free school meals to cover children aged seven to 11 would cost £610m a year, including a share destined for the education budgets of areas where power has been devolved.
“Sometimes we talk as if every packed lunch has a pot of hummus and some carrot sticks and muesli,” said Mr Clegg, adding that this wasn’t the case.
“I’m not pointing an accusatory finger at parents, but a lot of kids are going to schools with packed lunches which simply aren’t nutritious.
“I’ve seen some schools where kids turn up with a fizzy drink and a slice of white bread with chocolate paste on it.
“If you give that to a four or five-year-old, don’t be surprised if they can’t concentrate very well by the end of the school day.”
Mr Clegg said the move would save parents £400 for every child they have in primary school.
His party said the scheme would be introduced once the deficit had been eliminated, paid for “as resources allow” in line with projected public spending increases in line with economic growth.
The Lib Dems said pilot schemes showed a 23% increase in the number of children eating vegetables at lunchtime and an 18% drop in those eating crisps.