Sir Stephen Bubb, chief executive of the chief executives body Acevo, has called on the government to bring in new measures to help voluntary organisations suffering from the loss of public contracts.
The move follows a series of announcements in this week's Budget that are likely to help charities that rely heavily on donated income.
The measures included a reduction of inheritance tax on the estates of people who leave at least 10 per cent of their wealth to charity, and a move to allow charities to claim Gift Aid on claims of up to £5,000 a year without providing declarations.
"This has been an extremely good package - it contained many of the things we've looked for," said Bubb. "I'm optimistic that the government will come through in the same way for charities suffering from the loss of government contracts. It's certainly needed. We've not changed our view that the cuts will cost the sector £1bn this year."
Kevin Curley, chief executive of the local infrastructure group Navca, said most Navca members benefited from a range of different income streams and would be better off because of the measures announced in the Budget.
He added that the public services white paper was "enormously significant" for many of its members and that the recent announcement by Eric Pickles, the communities secretary, that "statutory force" would be used against local authorities that made disproportionate cuts to their voluntary sector budgets, was also a crucial step for charities.