An estimated one in four of the nation's children is brought up in poverty because their parents are unemployed, on low incomes or because they live in one-parent families.
The charity will officially launch its Pre-school Child Appeal in London on December 14 with a host of celebrities including agony aunt Claire Rayner, and children's author Althea Braithwaite. Dame Judi Dench is the patron of the appeal.
The alliance published a 12-page report this week, No Chance to Play, No Chance to Learn, which documents the plight of struggling families alongside pictures of needy children.
Margaret Lochrie, the alliance's chief executive, said: "Our research shows that of the 800,000 children under five attending our pre-schools, up to 200,000 need financial subsidies because their parents are on low incomes or unemployed.
"Only an estimated 14,000 children get any form of help from local authorities or other sources, which means that the rest must depend on our own charity fund-raising activities.
"Some of these families will get help from nursery vouchers, but this will be restricted to children aged four years. Our experience shows that children need opportunities for being able to learn through play at a much earlier age if they are not to be disadvantaged."
The report tells the story of three-year-old Robert, who lives on the Greenbank estate in Whitehaven, Cumbria.
Whitehaven used to be a successful seaport and mining town, but it is now a highly deprived area which has widespread second or third-generation unemployment.
Robert's father is unemployed. Last year his parents, and his brothers - aged five years and three months - were evicted from their home.
Robert is able to attend the Howhill playgroup two mornings a week only because of a grant made after an earlier appeal by the charity.
His mother says: "Twelve months ago, he was always crying and he would hardly speak. He would fight his brother and throw things. But now he's learning to share and has learned his colours and numbers, and he's getting really good at this. He's even singing songs at night - it's great."
Since the new appeal fund was opened earlier this year, 200 children have been helped. A grant of Pounds 25 can provide a child with one session a week for a term at a playgroup.