One in seven children is lost to homelessness, poverty and neglect, according to Barnardos.
The charity launches its Lost Childhood campaign today.
The charity hopes to get almost 60,000 people to join the campaign to help those children left behind.
CEO of Barnardos Fergus Finlay says they have also identified six short-term measures to help children.
He said: “Things like a dedicated public health system so that every child would be guaranteed five visits in their home by a community nurse during their first two years of life.
“Things like an extra free year in pre-school. Those kind of small practical measures.
“They are almost nothing in the scheme of things, but they would be the kind of things that would begin to make a real difference.”
Mr Finlay said thousands of children were living in hotels or overcrowded accommodation without space they need to live, play and grow.
Thousands more lived in poverty or languished on waiting lists for essential health services, such as speech and language therapy and mental health services.
It was obvious that children and childhood were not a priority in Ireland, he said.
“How is this OK? How do we as a country think this is OK?” Mr Finlay asked.
“For too long children have not been a priority politically and childhood itself has not been valued as it should be — the most important time of a person’s life.”
Mr Finlay said the community had a responsibility to ensure every child could reach their potential.