Ebenezer Azamati was "accosted" by a security guard when he tried to return to a seat he had earlier reserved before the discussion on 17 October.

On Saturday, he was cleared of any wrongdoing.

President of the society Brendan McGrath apologised for his "mistakes" and resigned.

Postgraduate student Mr Azamati, from Ghana, said his treatment made him feel "unwelcome in the union, Oxford and even the country".

After the charges against Mr Azamati were successfully appealed, Mr McGrath apologised to the Africa Society "for the distress and any reputational damage" to the student.

Helen Mountfield QC, representing Mr Azamati, had said there were ongoing talks with the union over what steps it could take to address the "failings" exposed by the case.

He added he had been asked by those present to bring the disciplinary complaint against him on behalf of a staff member but added he "should have recognised a wider obligation".

"The right response would not have begun with prosecution and apportioning blame; it would have addressed immediately the extreme distress of all involved," he continued.

Before signing his resignation, he added he had proposed "a full, public and independent review" of the union's policies in relation to disability, how it trains its staff and whether the current security system "is fit for the purpose of a student society".

The Oxford Union, which is independent from the university, has a tradition of hosting debates and speakers stretching back to 1823.

The university previously tweeted its support for Mr Azamati, and said it shared "the widespread outrage regarding the unacceptable treatment" of the student.