Johan Eldebo, the Senior Humanitarian Adviser at World Vision, told Premier that the charity is expecting a huge displacement from the city as fighting intensifies.
Eldebo said: "We are calling on all the actors involved to ensure that civilians who could get trapped in the middle of this crisis are protected from the fighting."
World Vision is among aid organisations who have expressed "deep concern" after a UN report revealed that Islamic State appears to be using tens of thousands of people, including children, as human shields in and around Mosul, where Iraqi forces are waging a large-scale offensive in order to take back control of the city.
UN Spokeswoman Ravina Shamdasani said: "Isil's depraved, cowardly strategy is to attempt to use the presence of civilian hostages to render certain points, areas or military forces immune from military operations, effectively using tens of thousands of women, men and children as human shields.
"Many of those who refused to comply were shot on the spot, and even among those who did comply, many of them - including 190 former ISF (Iraqi security forces) officers and 42 other civilians - were shot dead," she added.
Aid organisations have been unable able to approach the city to help those in need because of ISIS suicide bombers targeting aid workers, Eldebo explained.
"Access to Mosul itself is difficult," said Eldebo, "but World Vision is preparing to help those who are able to leave by providing water and shelter.
"According to the UN, several thousand people have managed to leave already. We expect that figure to rise once street fighting begins in central Mosul," he added.
The UN and rights groups believe that more than 200,000 civilians could be displaced during the offensive. Mosul is still home to more than a million people.