At the conference, Mr Corbyn praised Tower Hamlets council for helping to create a “fair and just society”.
Labour had put Mr Pappu in charge of governance scrutiny at the council, whose children’s services have been rated as inadequate, and was vice-chairman of the grants scrutiny committee.
Four Tower Hamlets schoolgirls aged 15 and one aged 16 were radicalised into going to Syria in 2014 and 2015 to join Islamic State.
Backed by the pro-Corbyn Momentum activist group, Mr Pappu was elected the black and ethnic minority officer for Young Labour in February.
He has been suspended by the national Labour party pending an investigation.