More than £55m has been deposited in a specialist savings account for small and medium-sized charities since its launch by the Charities Aid Foundation last November.
In August alone, £5m was invested in the Fixed Rate Selector Account, which is administered by Birmingham Midshires, a division of Halifax.
The account offers a fixed rate of interest for sums deposited for between three months and three years.
Tracey Reddings, executive director of financial services at CAF, said: "The Fixed Rate Selector Account allows charities to receive a rate of interest guaranteed to remain unchanged over a term that suits them best."
The account is open to voluntary organisations including faith groups, hospital trusts, friendly societies, clubs and housing associations. Deposits can vary between £10,000 and £10m.
Interest rates, which remain constant for the term of the account, varied from 4.59 per cent to 4.48 per cent in September. However, they can change on the first day of each month.