The decision to give Manchester charity Christie's the £6.5m it lost in the collapse of Icelandic banks while other charities still await news of their fate is perverse and unfair, according to the joint chairman of charity pressure group Save Our Savings.
Peter Hepburn, chief executive of animal welfare charity Cats Protection and a leading light of SOS, a group of 30 charities that lost £50m in failed banks, said he feared the decision "could signal unfairness ahead".
The Treasury is due to announce this week what action it will take to compensate the 30 charities.
But last week NHS North West gave £6.5m to Christie's, which raises £13m a year for cancer hospital The Christie after a strong campaign by the Manchester Evening News.
Hepburn said it would be "perverse and unfair" if Christie's were favoured over the rest of the SOS group and called for a consistent approach to all charities that have been lobbying the Treasury for full compensation.
"We should not be lulled into thinking the money for Christie's was pre-existing NHS money," he said. "It's all government money and the implication is that it was convenient for the Government to compensate Christie's because the hospital was already receiving public funding, so that channel was open."
He said the Cash Back for Christie's campaign had strengthened Christie's case, but said he suspected the charity had also benefited from further conversations with the Government. He said he was concerned that other SOS charities would lose out because they were not providing public services.
Hepburn said SOS would continue its campaign if the Treasury response was negative, but it would be "an appalling waste of donors' money" if the group was forced to take legal action.
Christie's dropped plans to seek a judicial review after recovering the money and withdrew from SOS.
Louise Hadley, head of Christie's, said: "Our priority is and always will be our patients, and that's where our focus needs to be.
"We feel for the other charities still awaiting the return of their funds and hope they receive compensation as soon as possible."
NHS North West said its support for Christie's was not at the expense of other NHS services.