A survey recently completed by the trust showed that in some cases as little as 2 per cent of the sale price from charity cards goes to charity, while 17.5 per cent is used to pay VAT and up to 50 per cent is retained by retailers.
The trust is leading more than 100 charities in the 'say no below 10 per cent' campaign. Members refuse deals with card manufacturers unless at least 10 per cent of the sale price will go to charity.
But several larger charities, including NSPCC and Cancer Research UK, whose deals with large retailers are lucrative in spite of single-figure percentage donations, have declined to take part in the campaign.
"I call on the larger charities to join," said Hilary Blume, director of the Charities Advisory Trust. "In the end there is more money to be made, and if that helps charities reach more beneficiaries it is worth fighting for."
The trust has used its second annual charity Christmas Card Awards to name the worst retail offenders and highlight the issue.
The Liz Dexter range of cards sold in Selfridges picked up the Scrooge Prize at the awards because only 2 per cent of the retail sale price goes to the Action Medical Research charity.
The trust hopes the campaign will achieve fair donations for all charities, but warns that legislation may be necessary.
"The amount of chocolate in a chocolate bar is regulated by the Trade Descriptions Act, but retailers are allowed to hang signs promoting their 'charity Christmas cards' even when very little goes to charity," said Blume.
NSPCC mail order manager Julia Evans said: "Whether people are buying their Christmas cards directly from a charity, a collective such as the trust's Card Aid, or buying cards which donate their royalties, the important thing is that they buy charity cards and help us to raise vital funds."