New documentary Destination Unknown arrives at a time when antisemitism is soaring and Holocaust denial spreading. Drawing on 13 years' worth of intimate interviews with survivors of the Shoah, conducted by its producer, Llion Roberts, the documentary is a powerful reminder of the pain and loss suffered by European Jewry, and a testament to the resilience of the Jewish people.

The film includes Jews who endured the camps, one who survived in hiding, a partisan, a Treblinka escapee, several who owe their lives to Oskar Schindler, and one who persuaded the German industrialist to switch production from enamelware to anti-tank grenades at his factory to save his workers. Their moving testimonies are filled with horror and hope, abiding grief, humanity, and the implicit call to never forget.

However, not everyone has embraced the film and Roberts believes that, in some quarters, apathy now surrounds the Holocaust. Film festivals, including Israeli and Jewish ones,all said no to programming Destination Unknown. “So you can't blame [just] the non-Jews,” says Roberts, who is not Jewish.

Connected to this alleged apathy, he suggests, is “the mortality of the survivors. The strong voices are going. They're dying.”

"Every day there is less survivors,” Ed Mosberg, a former prisoner at the Plaszow and Mathausen concentration camps featured on the film's poster, in his 90s, wearing a striped camp uniform, says from New York. He knows his time, like that of some of the other people interviewed in the film, will eventually come to an end. “But as long as I am alive, I will talk. I never stop.”

His family – he's been married to another survivor for 70 years and has three daughters – wish he'd slow down. “They are afraid that one day I will drop dead. But this is it,” he says defiantly. “If it happens, it happens."

Mosberg was the third survivor Roberts met during his first US research trip in 2003. “The Holocaust is part of his DNA now,” the producer says, and the feisty nonagenarian has made it his mission - “This is my duty and obligation,” he informs me - to keep the memory of his 16 murdered family members and the six million alive. His wife rarely talks about the Holocaust, and initially tried to hide her tattoo from their children. He never felt like silence was an option.

“Right after the war, people were ashamed that they survived. I'm not ashamed of it. I said, 'People have to know, not forget something like this happened.'” Nor, Mosberg adds, must they ever forgive “the barbaric murderers”; “Only the dead can forgive,” he says with a grief-fuelled anger undiminished by time.

While the UN designated January 27th as International Holocaust Remembrance Day, not a day passes when Mosberg doesn't remember. On his bedroom wall, photographs of his slaughtered relatives hang like religious icons. “When I get up in the morning, I stand and I look at those pictures,” he says. “When I go to sleep, I look at those pictures. I always think about it, because I lost the whole family."

Born in Krakow, in 1926, Mosberg attributes his own survival to luck. His family was financially well off and he insists that he didn't witness any antisemitism until the Germans invaded in 1939. When they were moved to the ghetto, in 1941, Mosberg (his father, an engineer, had already been killed) found himself in a two-bedroom apartment with his grandparents, mother, two sisters, and two aunts and their three children. They were cramped, but happy. “We were still together. We were alive.”

Systematic selections removed people from the ghetto, but their destination was unknown. “They [the Nazis] were telling people, 'When you go, take all your belongings, because you will be resettled.' And they resettled them – to the Belzec gas chambers. But no one knew, because no one came back.”

On March 13, 1943, the Nazis began to liquidate the ghetto. “I saw the murders that were committed,” says Mosberg, his voice cracking with emotion. He remembers Amon Göth, the commandant of Plaszow, played by Ralph Fiennes in Schindler's List, “running around shooting people”. They ripped a child from a woman's arms and “hit its head against a wall, killing it instantly.” Others were shot dead inside the knapsacks their parents had concealed them in. People too sick to walk were pulled from the infirmary and told that if they could make it the other side of the square, they'd live. “They were crawling on their hands and knees, and when they came to the other side, they were all shot."

The living walked from the ghetto to the Plaszow camp, 3kms away, where Mosberg was put to work in Göth's office, filing papers. He was a sadist beyond the reach of any actor, claims Mosberg. “I saw how he could shoot people without any reasons. Run with a whip, hitting people. Or [kill them] with his dogs [Ralf and Rolf]. When I saw him, I was always afraid. No one, in my mind, could have portrayed a person like this.”

Mosberg had arrived at Plaszow with his mother, sisters and a cousin. In 1944, his mother – a religious Jew who refused a piece of meat before she left him, because it was treif - was “taken to Auschwitz to the gas chambers.” They knew by then that the Nazis were killing people at Auschwitz-Birkenau, but they still didn't know how. No one, though, was under any illusions about what they were capable of. “You could see them killing people in Plaszow. I saw. They burned them on a fire outside."

Later, Mosberg found himself in a sweltering, airless cattle wagon, also bound for Auschwitz. However, when the transport arrived, it sat on the rails for a night, because “they were too busy at the crematorium. So they never unloaded us and they took us to Mathausen.” He worked in the quarry, where exhausted prisoners ascended and descended 186 steps, carrying rocks weighing up to 50Kg. “If somebody stopped for a moment, they'd push them to their death. Or they'd beat you. Or they'd shoot you,” says Mosberg. “Mathausen and Gusen - they were the two worst concentration camps, and they were classified that way by the Germans.”

Mosberg's memories are vivid; his pain and anger heartbreaking. After talking to Roberts about the murder of his sisters at the Stuthof camp, a day before liberation, he fell ill. “His blood pressure went through the roof,” Roberts recalls. “He had headaches, migraine.” I ask Mosberg how he feels when he puts on the striped camp uniform today.

"I don't feel anything,” he says bluntly. “The uniform is for the other people, not for me.”

His harrowing experiences are undeniable and yet there are still those who seek to punch a hole in the Holocaust story and question the veracity of survivors. Mosberg says he would never talk to Holocaust deniers. If he did meet one, though, he knows what he would do.

“If I could get a guy, I would invite him to meet me. You know where? I would meet him at the top of the quarry in Mathausen, and I would hold his hand, and I would jump with him, together."

Destination Unknown opens June 16