Ron Jones, who marked his centenary on 30 April, volunteers for up to six hours a day at his local supermarket in Newport, south Wales.
Grandfather-of-two Mr Jones, from Bassaleg, Newport, has been collecting for the Poppy Appeal since 1981.
He was called up to fight in 1940 and served as a lance corporal in 1st Battalion Welch Regiment in the Middle East.
Mr Jones was captured in Benghazi in 1942 and, after nine months in Italy, was transferred to forced labour camp E715, part of the Auschwitz complex.
After two years of being held at the camp, he was forced to join the "death march" of prisoners across Europe in 1945.
He was freed by American troops and finally returned home to Newport and his wife Gladys in May 1945, having dropped from 13st to just 7st.
Mr Jones worked at the city's docks until his retirement in 1980, then began collecting for the Poppy Appeal the following year.
"I've been selling poppies for about 30 years, I go down to Tesco every year for a fortnight, practically every day," he told the Press Association.
"I like to do a lot for the British Legion as we help dependants, we help the boys coming back from Afghanistan.
"If they need help, I'm there.
"I've made as much as £15,000 occasionally but normally we get up to nine or ten thousand."
When asked whether he would ever retire from his role, Mr Jones replied firmly: "No".
The pensioner admitted that he has become "a bit of a celebrity" at the Tesco on the Harlech Retail Park where he sells poppies.
Customers come in each year looking for him, with one woman driving from London to Newport to buy a poppy from Mr Jones.
"She put £20 in my box, that's what happens," Mr Jones said.
He usually volunteers for three hours each day but takes on a double shift, lasting for six hours, for three days of the appeal.
Last week, he attended the launch for the 2017 Poppy Appeal in Newport and refused a chair, standing instead for the 45-minute ceremony.
Mr Jones, whose wife died in 2005, said the Legion had been there for his friends who returned home after the war and needed help.
He described how he was called up in September 1940 and was sent to Cairo, Egypt, in 1941.
In January 1942 he was captured by the Germans and transferred to Auschwitz, where he spent two-and-a-half years.
During his time at the Nazi death camp, he worked alongside Jewish slave labourers at IG Farben's infamous chemical factory.
"When they got desperate they sent us out. I marched, I was on the death march from Poland back to Austria," he added.
"Seventeen weeks on the road, pulling vans at night time and bitterly cold, no food.
"We lost about 100 blokes who died on the road but I'm still here."
Lynne Woodyatt, community fundraiser for The Royal British Legion, paid tribute to Mr Jones as "a legend".
"He's one of our key volunteers and an ambassador for the appeal," she said.
"He does supermarket collections for us, he's quite a celebrity.
"The young generation love to interact with him and he loves to get them involved.
"He's so generous and the Legion is quite close to his heart."
Mr Jones features in a film called The Poppy Seller, released on 11 November, and has donated the payment for his appearance to The Royal British Legion.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies