The Fundraising Standards Board is set to hold a meeting with the Big Give after receiving complaints from charities about the Big Give Christmas Challenge.
The FRSB confirmed several charities have complained to it about the online match funding scheme, which took place last week and raised more than £10m for 424 charities.
Some charities said they were disappointed with the scheme last week, with some fearing it had put donors off giving.
Among their complaints was the fact that the website had crashed because of high demand on Monday, and that the match funding had run out within a few minutes of the site opening for donations on some mornings.
Alistair McLean, chief executive of the FRSB, said it had been contacted by both member and non-member charities about the problems they had experienced when trying to raise money through the challenge last week. He declined to confirm the exact number of complaints.
"We have been contacted by a number of charities that are clearly upset about the Big Give Christmas Challenge," he said. "Although the Big Give is not a member of the FRSB, I have made contact with it and hope to arrange a meeting to discuss the issue."
Helen Cable, operations manager for the Big Give, confirmed it had received an email from the FRSB.
"We’re more than happy to have a meeting with the board," she said. "We don’t feel we have anything to hide. We know we’ve got a few issues to sort out and, if they can help, that would be great."
The challenge exceeded its £10m fundraising target by the end of last week, and charities would be able to continue to raise money using match-funding pledges they organised individually with donors until 22 December, said Cable.