Christian Aid, World Vision and Tearfund are expressing concern over Russian plans for evacuation routes in east Aleppo.
Over all 35 different groups say an immediate 48 hour ceasefire would be better for those trapped, and could allow help to get in.
The group has released a statement saying: "We are extremely alarmed at Russia and Syria's joint proposal to set up so-called "humanitarian corridors" out of eastern Aleppo.
"We consider the proposal deeply flawed on humanitarian grounds and consider it warning for the International Syria Support Group (ISSG) to urgently step up efforts to end the use of brutal siege tactics and illegal attacks on civilians."
It goes on to say that: "A true humanitarian operation would not force the people of Aleppo to choose between fleeing into the arms of their attackers or remaining in a besieged area under continued bombardment.
"No one should be forced to flee or remain, and measures must be put in place for the UN to ensure and monitor the safety and protection of anyone voluntarily evacuating."
Louise Finan, Middle East advocacy officer for Christian Aid, told Premier that the situation is desperate.
She said: "There should never be... a forced displacement because a warring party is about to launch an attack on your home, civilians have the right to stay where they are."
Ms Finan went on: "Our concern will be that it will make viable the idea that anybody left behind is a miliatary target, which is completely against international humantarian law."
Other groups that have signed include Hand in Hand for Syria, Islamic Relief USA and Doctors of the World UK.
Listen to Premier's Alex Williams speak to Louise Finan here: