The figures, to be revealed in the FRSB's annual report, will cover complaints made either directly to charities or passed on to them by the FRSB to see whether they can resolve them themselves.
The FRSB is to decide at its next meeting in December whether and how it will release figures relating to complaints that charities are unable to resolve themselves and which are dealt with by FRSB officials or, in some cases, by an adjudication of the board itself.
A spokeswoman for the FRSB declined to give any figures after its meeting last week. Its complaints system was launched to the public in February this year. Nearly 700 charities have joined the scheme so far.
One source close to the FRSB expressed frustration that it was providing no figures at this stage. "I don't understand why it can't explain the reasons it doesn't want them to be made public yet," he said.
Joe Saxton, chair of the Institute of Fundraising, said: "The FRSB is overcautious - and quite rightly so given its history so far of announcing things too early and then having to delay events."