In the past week, the United Nations World Food Programme, the World Land Trust, and Cancer Bridge have all admitted that donations have slumped since the disaster.
Donations to the World Food Programme's operations in Africa were 21 per cent lower in January, than in January 2004. Globally, donations to its work in Africa constituted just 8 per cent of the agency's total income, compared with 20 per cent a year ago.
The World Land Trust says it has had its worst two months ever, with virtually no donations since Christmas. Chief executive John Burton said: "We always have a slight drop in January and February, but this year was off the scale."
The charity expected 20 or 30 donations following a BBC TV programme featuring Bill Oddie at one of the trust's reserves in Patagonia. But in the 10 days since the programme was broadcast, just one had come in.
"To get nothing back is very serious and there is a clear link with the tsunami," Burton added.
Meanwhile, Cancer Bridge in Northumberland has had to cut the number of patients it helps because of a drop in income, which chief executive Pat Reed attributes, at least in part, to the tsunami.
She said: "The cheques that we expected to receive in January have been noticeable by their absence. We were also promised a donation of £5,000 before Christmas by a private company, but have just received a letter saying it has given a substantial sum to the tsunami appeal instead.
"It's impossible to quantify precisely how much money we have lost as a result, but it's probably near £10,000 or £15,000."
At the same time, some charities that have received vast chunks of tsunami aid money admit they are struggling to spend it.