In its response to the Treasury’s proposals to make 10 per cent savings across all government departments in the year 2015/16, the commission says it cannot make cuts "without impacting on the fulfilment of our statutory responsibilities", which would have a negative effect on public trust in the sector.
The response to the Treasury, from Sam Younger, chief executive of the commission, says: "There is no more fat to cut. Everything we do now is in fulfilment of our statutory responsibilities."
It also reiterates previous suggestions made by the commission that it could charge charities for its regulatory functions or take money from Gift Aid.
In order to meet cuts of 10 per cent, Younger says, the commission would have to consider reducing the serious investigations it carries out. "We do not believe this would be acceptable to parliament or to the public," the letter says.
Instead of cutting its investigatory work, Younger says, the commission would have to cut its "lower-risk facilitative work", such as giving consents to charities to amend their governing documents or to sell land or property.
Younger warns that the cuts would also result in slower response times in registering charities. "All of this would make charities less efficient and adaptable, and have a negative impact on the operations of charities and on public trust and confidence in the commission and the sector," says Younger.
The commission says it would welcome government consideration of a new funding model to give it greater stability.
Possibilities include a top-slicing of the £1bn a year claimed in Gift Aid, a direct levy on charities and deriving funding directly from parliament.
Younger adds: "Any change to the way the commission is funded is likely to require primary legislation and so would not have any impact on 2015/16; we would nonetheless welcome a debate on our long-term funding needs."