The astonishing story of a US army veteran who was said to have been found living in a remote Vietnamese village 44 years after his fighter plane was shot down and he was missing presumed dead has been exposed as a hoax.

Unclaimed, a documentary by Emmy-award winning Canadian filmmaker Michael Jorgenson, claims that an old man living in a remote Vietnamese village is former Green Beret, Sgt John Hartley Robertson, who died during a classified special mission over Laos in 1968, according to military records.

His body was never found and his name was etched alongside those of 60,000 other fallen soldiers on the Vietnam memorial in Washington.

The gripping tale raised the possibility that the American POW escaped from his Vietnamese captors and began a family in secret with a local woman, leaving his wife and two children grief-stricken back in the US.

However, Dan Tan Ngoc, the 76-year-old man who claimed to be Robertson has now been revealed to be a fraud.

According to the MailOnline, he came to the attention of US personnel in Vietnam in 2006 after he repeatedly tried to con members of the Vietnam MIA/POW community into believing that he was Robertson.

Under interrogation, he is said to have subsequently admitted that he was not Robertson but a Vietnamese citizen.

In 2008, he was taken to the US embassy in Phnom Penh, Cambodia, where he was fingerprinted.

A February 2009 report by the FBI confirmed that that Ngoc's fingerprints did not match those in Robertson's official records.

The revelations come hours after the release of Unclaimed, which alleged that a vet hero had been discovered over four decades after his apparent death.

In the film, Ngoc convinced viewers that his helicopter had been shot down and he had been captured by the North Vietnamese.

He was unable to remember his birthday, his American children's names, or how to speak English.

"They locked me up, high in the forest, in a cage," he said through an interpreter. "I was in and out of consciousness from torture and starvation. The North Vietnamese soldier hit me on the head with a stick, shouting, 'American!'

"Then he would hit me even harder; I thought I would die. I never said anything, though they beat and tortured me."

The emotional climax saw him reunited with a man he trained with in the 60s and his 80-year-old sister, Jean Robertson Holly. Both claim to have recognised his Robertson on sight.

Reports suggest that Ngoc has been attempting to impersonate Robertson since 1982.

The FBI believes that these attempts to claim the identity of a MIA soldier were attempts to defraud the US government of money in military back-pay.

It is thought that Ngoc has possibly scammed tens of thousands of dollars from well-meaning veterans.