The former Reading and West Bromwich Albion technical director joined Celtic on a temporary basis in June with responsibility for overseeing the current transfer window, which closes on 2 September.
Hammond replaced Lee Congerton, who left the Scottish champions in May to rejoin former manager Brendan Rodgers at Leicester City.
Celtic’s transfer strategy has come under scrutiny in the wake of their Champions League exit against Cluj and Lennon insists the situation is being addressed. “If people want to be critical about the recruitment then I understand that,” said Lennon.
“We have brought in some very good players over the years and are hoping to do that again. It is an issue because a void was left and it’s not been filled yet. We have a rebuilding job on the recruitment side. We are trying to do that and Nick is working to rebuild the recruitment department. It’s been difficult with so much change and that’s the part the public don’t see. We are working hard in the background.”