"So far as is known, the first accusation against the Germans of the mass murder of Jews in war-time Europe was made by the Polish Jew Rafael Lemkin in his book Axis Rule in Occupied Europe, published in New York in 1943. Somewhat coincidentally, Lemkin was later to draw up the U.N. Genocide Convention, which seeks to outlaw "racialism". His book claimed that the Nazis had destroyed millions of Jews, perhaps as many as six millions. This, by 1943, would have been remarkable indeed, since the action was allegedly started only in the summer of 1942. At such a rate, the entire world Jewish population would have been exterminated by 1945."
Every word is wrong. Lemkin was not the first to expose the Nazi genocide, in fact he can be seen as one of the later ones to point it out. The first ones to bring the world's attention to the unfolding Holocaust was the Polish Resistance, and various Jewish groups in Occupied Poland, two sets of organizations that were acrimonious in regards to their conduct with each other and would have surely never "conspired" in any way together.