The company estimates that the financial viability of at least two-thirds of charities with long-term capital investments is under threat because of the recent sharp downturn.
As a result, some have resorted to "selling the family silver", said Close's charity development manager Clive Paine. Charities are selling shares and property, moving into cheaper premises, remortgaging their property and even moving entirely out of equity investments and into cash.
Unless conditions improve, some may be forced to close, the firm says.
Martin Smith, chief executive of Close Wealth Management, said: "With poor stock market returns, it is estimated that UK charities had 10 per cent shaved off their combined wealth last year alone, which was then estimated at £30 billion."
"Peripheral" health charities such as mental health care organisations and ex-servicemen's charities are under financial pressure and could be forced to merge, claims Paine.
He said that many charities were deserting equity-dominated investments for fixed interest investments such as bonds and gilts. "There is a 40 per cent differential between the performance of equities and fixed interest since the end of 1999," he said.
Many trustees were also too slow to react to the current crisis. Investment committees needed to meet three times a year, he said.