The scale of the Nazis' attempt to eradicate Europe's Jewish population could far exceed what historians have long believed to be the case, according to a group of academics from the United States Holocaust Memorial Museum.

As part of a 13-year project to catalogue the sites of Nazi atrocities and build a comprehensive map of the Holocaust, researchers have found evidence of 42,500 Nazi "killing centres", ghettoes, forced labour camps and other sites of persecution and murder.

The list, which covers the period between 1933 and 1945 and the different areas occupied by the Germans, includes camps where women were forced into prostitution or made to have abortions, as well as places where prisoners were forced to construct war equipment.

While major concentration camps such as Auschwitz are well known, the list includes myriad unknown Nazi sites, including an astonishing 980 concentration camps and 1,150 Jewish ghettoes. The research team had anticipated finding evidence of around 7,000 Nazi sites; they have now identified six times that number.

The scale of sites identified on their map has led the project leaders, Geoffrey Megargee and Martin Dean, to suggest that the Nazis could have brutalised up to 20 million people in the years before and during the Final Solution. They are not due to complete the project until 2025, but have already published two volumes of findings work.

Dr Dean told the New York Times that their findings also suggested that ordinary Germans must have known about what the Nazis were doing, since "you literally could not go anywhere in Germany without running into forced labour camps, PoW camps, concentration camps," he said. "They were everywhere."

Dr Megargee said the results of their work were shocking. He told the Independent: "We are putting together numbers that no one ever compiled before".

"The Nazis' determination to systematically wipe out the Jews of Europe is well documented, but this new research demonstrates the horrifying scale of their murderous intentions and the apparatus put in place to achieve them," said Karen Pollock, chief executive of the Holocaust Educational Trust.

"When this unique research project concludes in 2025 there will sadly only be a handful of survivors left to share their testimony, making it even more important for us to continue to further our understanding of what happened during the darkest period in our shared history."