The Directory of Social Change's first ever Funders' Almanac shows 52 per cent of central government grant schemes are currently for two to three years, compared with 29 per cent in 2006/07.
One-year grant funding has dropped from 47 per cent in 2004/05 to 14 per cent in 2008/09.
"Based on the assumption that longer funding periods are beneficial to voluntary organisations, what we are seeing is quite promising," the almanac says.
However, funding for longer than three years, which constituted 10 per cent of central government funding in 2004/05, is now negligible.
In 2006, the Government promised that three-year funding would become the norm for third sector organisations.
Ben Wittenberg, director of policy and research at the DSC, said that one-year funding was sometimes legitimate, but in areas such as health "three-year funding doesn't sound very long at all".