Ms Levi was deported by the Nazis from her Hungarian home at the age of 20, forced to labour in a munitions factory and sent on a death march as the Allied forces approached.
It was important, she said, that politicians raised awareness about the Holocaust.
Mr Cameron noted that with fewer survivors around to tell their stories, "it is in fact more important than ever that we recall what happened and the terrible consequences.
"As well as recalling the dreadful suffering and murder in the ghettos and camps, we must also remember the genocide and hatred in our world today.
"From learning our history, we must pledge that it should not be repeated."
For more on Holocaust Memorial Day 2011 see our dedicated HMD page
