The figures, which have been broken down by constituency and local authority, show 260 children living in poverty are set to lose out in Theresa May's constituency of Maidenhead.
It comes as Nick Clegg is set to unveil a new, hard-hitting poster attacking Theresa May's decision to scrap free school lunches.
The Liberal Democrats have also calculated that under Conservative costings of just under 7p per child's breakfast, each child could expect to receive either half a boiled egg, one slice of bread with 12 baked beans or 37.5 cornflakes and 100ml of semi-skimmed milk.
Commenting on the figures, Nick Clegg said:
"Theresa May's cruel and illogical decision to take away free, hot lunches for all infants will hurt hundreds of thousands of Britain's poorest children.
"It's clear that the reintroduction of means-testing for school lunches will mean many children losing out on what could be the only hot, nutritious meal that they receive each day.
"Theresa May is not only risking the health of some of our youngest children, but she will also create terrible inequality in the classroom.
"The Conservatives' cynical promise of a free breakfast is clearly not designed to reach all children because they have set aside a meagre 7p per breakfast per child. That's the price of half a boiled egg or just one slice of bread with 12 baked beans.
"Theresa May insists she wants to govern for everyone. But her regressive cutting of free school lunches is clear evidence she is prepared to ignore some of the poorest and most vulnerable children in our society.
"Just because the youngest don't vote, it doesn't mean that Theresa May should simply cast them aside."