Pro-democracy camp lawmakers questioned his nationality and demanded the "declaration of renunciation", a document issued by the UK Home Office.
Held on 11 October 2016, the special forum allowed candidates to present their manifesto and answer questions from other members.
As the second most senior member who did not run for president, Abraham Shek took the chair for the rest of the election.
Opposition councillors boycotted the election and walked out the chamber without attending the vote count.
Before adjourning the meeting, Leung said he accepted the position with a heavy heart and hoped there would be more communication across both camps.