A former Auschwitz guard has pleaded for mercy in a bid to avoid jail for his role in the murder of more than 300,000 people.

Oskar Groening​, known as the “bookkeeper of Auschwitz”, was sentenced to four years in prison in 2015 for being an accessory to murder at the concentration camp in Nazi-occupied Poland.

But the 96-year-old German has not yet started his sentence due to a dispute about his health. He has now filed a plea for clemency, a regional justice spokesman said.

​In December, Germany’s constitutional court ruled Groening must go to jail, rejecting arguments from his lawyers that imprisonment at his advanced age would violate his right to life and physical safety.

Groening’s court battle was seen as one of the last major trials related to the Holocaust, in which six million Jews were murdered by Adolf Hitler’s regime.

Prosecutors said Groening – who did not kill anyone himself while working at Auschwitz – had helped support the regime responsible for mass murder by sorting bank notes seized from trainloads of arriving victims.

Groening admitted he was morally guilty for the work he carried out at Auschwitz, which included sending bank notes he found in Jews’ luggage to SS offices in Berlin, where they helped to fund the Nazi war effort. But he did not admit participating in any crimes.

However, the court that convicted him ruled he was part of the ”machinery of death", helping the camp function and collecting money stolen from the victims to help the Nazi cause.

Remembering the Holocaust Show all 16 1 /16 Remembering the Holocaust Remembering the Holocaust 80,000 shoes line a display case in Auschwitz I. The shoes of those who had been sent to their deaths were transported back to Germany for use of the Third Reich Hannah Bills Remembering the Holocaust Barracks for prisoners in the vast Auschwitz II (Birkenau) camp. Here slept as many as four per bunk, translating to around one thousand people per barracks. The barracks were never heated in winter, so the living space of inmates would have been the same temperature as outside. Hannah Bills Remembering the Holocaust Hannah Bills Remembering the Holocaust Sign for the Auschwitz Museum on the snowy streets of Oswiecim, Poland Hannah Bills Remembering the Holocaust The Gateway to hell: The Nazi proclamation that work will set you free, displayed on the entrance gate of Auschwitz I Hannah Bills Remembering the Holocaust A disused watchtower, surveying a stark tree-lined street through Auschwitz I concentration camp Hannah Bills Remembering the Holocaust Stolen property of the Jews: Numerous spectacles, removed from the possession of their owners when they were selected to die in the gas chambers of Auschwitz Hannah Bills Remembering the Holocaust A sign bearing a skull and crossbones barks an order to a person to stop beside the once-electrified fences which reinforced the Auschwitz I camp Hannah Bills Remembering the Holocaust The peace and the evil: Flower tributes line a section of wall which was used for individual and group executions Hannah Bills Remembering the Holocaust Life behind bars: Nazi traps set to hold the Third Reich’s ‘enemies’. In Auschwitz’s years of operation, there were around three hundred successful escapes. A common punishment for an escape attempt was death by starvation Hannah Bills Remembering the Holocaust Burying the evidence: Remains of one of the several Auschwitz-Birkenau gas chambers Hannah Bills Remembering the Holocaust Hannah Bills Remembering the Holocaust The three-way railway track at the entrance to Auschwitz-Birkenau camp. This was the first sight the new camp arrivals saw upon completion of their journey. Just beside the tracks, husbands and wives, sons and daughters and brothers and sisters were torn from each other. Most never saw their relatives again Hannah Bills Remembering the Holocaust A group of visitors move through the Auschwitz-Birkenau camp. Viewed from the main entrance watchtower of Auschwitz-Birkenau Hannah Bills Remembering the Holocaust "The Final Solution": The scale of the extermination efforts of the Nazis at Auschwitz-Birkenau can be seen by comparing the scale of the two figures at the far left of the image to the size of the figure to the left of the railway tracks' three point split Hannah Bills Remembering the Holocaust Each cattle car would transport up to one hundred people, who could come from all over Europe, sometimes from as far away as Norway or Greece. Typically, people would have been loaded onto the trucks with around three days food supply. The journey to Auschwitz could sometimes take three weeks. Hannah Bills

Groening's last legal appeal was rejected at Germany’s highest court in December. But the Federal Constitutional Court noted German law allows for prison sentences to be interrupted if a prisoner’s health deteriorates significantly.

Doctors have previously declared Groening fit to go to prison as long as there is appropriate medical care.

Christian Lauenstein, spokesman for the justice ministry in the northern state of Lower Saxony, where Groening’s 2015 trial took place, said his plea for mercy had been passed on to public prosecutors.

He added: “A plea for clemency does not have a delaying effect such as on starting the prison sentence.”