Umbrella body the NCVO is seeking cast-iron guarantees from all parties during the General Election campaign that they would bring back the Charities Bill in the next Queen's Speech.
The Charities Bill was one of 10 bills terminated because of the dissolution of Parliament as a result of the election being called last week. Another was the National Lottery Bill, which was to formally create the Big Lottery Fund.
NCVO chief executive Stuart Etherington lamented "one of the most disappointing weeks for the UK charity sector for a long time. The Bill and its proposals are backed by a powerful coalition of charities, thousands of other voluntary organisations besides and by the three main political parties. Yet this Bill will still not become law."
Geraldine Peacock, chair of the Charity Commission, said: "We've very disappointed that the Bill has been lost."
Home Secretary Charles Clarke told a charity audience last month that the Government wanted to work with the other parties to ensure the Charities Bill made it onto the statute book, even if there was a dissolution. But this has not happened.