The National Missing Persons Helpline is feeling the pinch as a result of the millions being ploughed into the DEC tsunami appeal, after its own bids for funding failed to bear fruit.
The charity is seeking funding to employ someone to run a section on their website dedicated to people missing since the tsunami, and to recover the extensive costs of supporting their families through its free helpline.
It sent an appeal letter to 650 grant-giving trusts three weeks ago, but has so far received only rejections.
Co-founder Janet Newman met officials at the Foreign Office last week, but was not promised any funds.
"We are totally stretched at the moment," said Sophie Woodforde, the charity's head of press. "Funders must realise that life continues for charities such as ours."