Schemes to support vulnerable children and their families could be axed, and some smaller charities may close, because of millions of pounds worth of cuts.
The Children's Fund, which is used to provide programmes for disadvantaged five to 13-year-olds and is one of Chancellor Gordon Brown's pet projects, had an original budget of pound;200 million.
But project leaders say only pound;140m has gone into the system and are demanding to know where the rest of the money has gone.
As The TES was going to press, ministers pledged an additional pound;20m in the coming year but made no reference to any future funding beyond 2005.
Schemes such as after-school clubs, mentoring and counselling programmes and support for youngsters at risk of domestic violence and abuse may now be scaled down or closed altogether in many parts of the country.
The cuts mean that contracts drawn up between schools, local authorities and charities to lay on projects will have to be broken.
One project manager, from east London, said: "This move is contrary to all government statements about tackling child poverty. It is effectively removing the preventative support network that follows children beyond Sure Start. No one is able to tell us where the money that was promised to us has gone."
In a letter to programme managers last week, Anne Weinstock, director of the Department for Education and Skills' supporting children and young people group, acknowledged budget difficulties.
She added: "Final decisions on that year will not be taken until we have consulted and discussed how best to hande the situation and until we know the result of the 2004 spending review."