The Royal British Legion said it had begun a high-level internal investigation into whether Sir John, a decorated Falklands hero, had abused his position with the charity.
Legion Director General Chris Simpkins said:
The Royal British Legion has a code of conduct which addresses the issue of conflict of interest.
The honorary position of National President falls within this code and should not be used for commercial gain or in order to gain access to politicians and senior military figures for purposes unrelated to his position as National President.
The list of guests invited to attend the Festival of Remembrance, and the seating arrangements, are administered internally without influence by the National President.
The President does not have any personal guests in his box at the Festival in which he entertains senior politicians and military personnel as guests of The Royal British Legion.This matter will be referred to the Legion's Governance Committee for review. The findings of the Governance Committee will be reported to the Board of Trustees for any necessary action.
More top news
Five Palestinians were reportedly shot dead by Israeli soldiers after a fresh spate of clashes broke out in the conflict-ridden region.
This weekend: Patchy rain in the northwest, dry and bright elsewhere.
Former ITN newscaster Gordon Honeycombe has died aged 79 in Australia, his family has said.