Arts minister Estelle Morris says she is fighting the Treasury to prevent the loss of Gift Aid on entrance fees to museums and galleries.
The existing loophole in the Gift Aid regulations has brought millions of pounds to the arts sector because it has been able to claim Gift Aid on entrance fees by treating them as donations.
The arts sector has fought a rearguard action since Chancellor Gordon Brown announced in his Budget in March that he would close the loophole.
At last week's Funding the Future conference, Morris said: "As Minister for Arts I'm with you against the Treasury rather than with the Treasury against you." She said she had told ministers and the Treasury that "the voluntary sector can't take this level of turmoil and instability".
But Morris added that the Gift Aid revenue stream on entry fees would have to be found elsewhere, because the Inland Revenue could not be seen to be endorsing the use of the loopholes in the way museums and galleries had.