Barnardo's has launched an emergency appeal for donations in the face of an expected £3m shortfall in fundraising income this year.
Chief executive Martin Narey said the situation was "extremely worrying".
"Unless we can raise the funds we need by 31 March, I am wondering how we will continue to support those on our own doorsteps who need us most," he said.
Narey blamed the shortfall on the recession and the decline in house and share prices.
He said the value of wills, the children's charity's biggest source of voluntary income, had plummeted by £1.2m.
"Altogether this year we will spend about £3m more than we have coming in," he said.
"We're under real pressure. This year, much of our income has dried up."
Asked about the effects on projects and jobs if the shortfall was not addressed, a spokeswoman said:"Barnardo's is not looking to close projects, but we must remain vigilant in this difficult economic time."
Barnardo's generated £214m in the year ending 31 March 2009, £1m less than the previous year. It spent £212m.
The biggest source of income is fees and grants for services, yielding £127m. Voluntary income contributed £47m.
Last month, Christian Aid opened what it called an "unprecedented" appeal to raise £1.5m. It is making about 80 posts redundant.