The event, set for Oct. 11 in Los Angeles, was intended to raise money for the Adopt-A-Minefield campaign, the Daily Mirror said. Heather Mills McCartney helped found the charity.
Adopt-A-Minefield declined to comment on the reports Friday and would not say whether the event had been canceled.
British newspapers reported that McCartney was considering making a donation to the organization to compensate it for the cancellation.
Stuart Bell, McCartney's spokesman, confirmed that McCartney would be making a donation, although he declined to comment on the exact sum.
McCartney, 64, and Mills McCartney, 38, announced their separation in May after four years of marriage. They have begun divorce proceedings in an increasingly acrimonious split. The couple have a 2-year-old daughter, Beatrice.
The former Beatle announced his decision not to attend the gala in July, saying in a statement that he would not be able to attend "given the current circumstances."
Last year's gala in Los Angeles, hosted by the couple, raised some $3 million for minefield clearance and the rehabilitation of land mine victims.