The charity says medicines and aid are not getting in because of Israel's ground offensive and air strikes.
Since the violence began two weeks ago more than 500 Palestinians and 20 Israelis have been killed.
Smoke rises after air strike in Gaza
Policy and Advocacy Officer for Israel and Palestine at Christian Aid, William Bell, told Premier's News Hour: "Some of the medical relief organisations that we support are able to get out, albeit in a pretty precarious situation and often under fire, to offer some immediate assistance.
"A lot of the support that we're going to be able to give and which we're preparing for is of course once a ceasefire is in place."
A damaged Gaza building after Israeli air-strike
Palestinian walks through rubble after Israeli air strike
On Monday afternoon Israeli tank fire directed at a hospital in Gaza killed at least five people and left dozens wounded.
Israel says it is protecting itself from constant rocket fire coming from militant group Hamas.
A rocket is fired into Israel from Gaza
The UN Human Rights Council is planning an emergency session on Wednesday in response to the crisis.
Meanwhile Pope Francis has offered his support to a parish priest in Gaza.
The Pontiff told the parish priest of Gaza, Father Jorge Hermandez, he was keeping the region in his prayers.
Listen to Policy and Advocacy Officer for Israel and Palestine at Christian Aid, William Bell, speaking to Premier's News Hour here: