White nationalists who have been flocking to genetic ancestry tests to prove their 'whiteness' are being disappointed.

American's fascination with heritage has seen a boom in the genetic testing industry - which now offers consumers the chance to learn their ancestry with a simple 'spit test' for just over $100.

While the vast majority of users are simply curious about where their ancestors came from, white supremacists, neo-Nazis and nationalists have reportedly been using the tests as a way of proving how 'pure' they are.

And when around two thirds learned they weren't as white as they believed they were, the reactions were not pretty.

White supremacist Craig Cobb tries to tune out the 'statistical noise' that reveals his genetic makeup is 86 per cent European and 14 per cent Sub-Saharan African in 2013

Many questioned the legitimacy of the results while some even claimed it was a Jewish conspiracy 'that is trying to confuse true white Americans about their ancestry,' according to a new study, by sociologists Aaron Panofsky and Joan Donovan who analysed posts on neo-Nazi website Stormfront, according to StatNews.

Others tried to rationalize away the results saying they did not matter if they were truly committed to being a white nationalist or if they could pass the 'mirror test.'

'They will say things like, 'If you see a Jew in the mirror looking back at you, that's a problem; if you don't, you're fine,' said Panofsky, a sociologist of science at UCLA's Institute for Society and Genetics.

American's fascination with heritage has seen a boom in the genetic testing industry - which now offers consumers the chance to learn their ancestry with a simple 'spit test' for just over $100

Both 23 and Me, and Ancestry.com have become very popular in recent years

One of the most famous instances of a white supremacist rejecting his genetic test results when they were not in his favor, came live on daytime television.

Craig Cobb, who once tried to turn a small North Dakotan town into a 'white enclave', underwent a DNA test on the British show, The Trisha Show.

Goddard, who is black, announced the results of the DNA Diagnostics test to the whoops of her studio audience, as she revealed Cobb was 14 per cent Sub-Saharan African heritage.

On hearing the results Cobb, who insists he is not a white supremacist but a Creator, a religion which favors 'racial awareness', immediately dismissed the news that genetically he is 14 per cent Sub Saharan African, 86 per cent European, as 'statistical noise.'

He said: 'I tell you. Oil and water don't mix.'

With a fixed grin Cobb, he shook his head and tried to wave these ones away as Goddard insisted: 'You have a little black in you.'

'You've got a little black in you bro': Trisha moved in for a fist bump undeterred by her guest's evident reluctant to meet her hand or eye during his appearance on her show in 2013

If at first you don't succeed....Cobb will make sure you never do. Trisha is left hanging by her guest's refusal to make contact

When the British host tried to fist bump her guest, with the words, 'So there you go bro,' Cobb visibly recoiled and twice refused to meet her touch.

HOW WAS THE STUDY CONDUCTED? Analysts from the University of California, Los Angeles, sifted through 12 million posts on Stormfront, written by over 300,000 members, to search for terms like 'DNA test,' 'haplotype,' '23andMe,' and 'National Geographic' in the study. The team reduced their results down to 70 discussion threads in which 153 users posted their genetic ancestry test results, with over 3,000 individual posts and assessed the results, according to Stat News. Advertisement

Cobb later dismissed the validity of the test, telling DailyMail.com: 'I agreed to the test because I assumed it was science.' Instead, he said, it was a scientifically bankrupt procedure, the product of 'craven and debased executives,' whose 'goal is to shock.'

His reaction is typical of white supremacists stunned to learned they are actually of mixed heritage, the study finds.

Around two thirds of nationalists who took the tests and posted on Stormfront were disappointed with the results.

Although it is surprising they admitted the results at all as Stormfront demands its members must be '100 percent white European, not Jewish.'

Cobb once tried to turn a small North Dakotan town into a 'white enclave'

Some of the newer members were kicked out of the forum when they revealed their results, the study found, but many others were actually comforted by their fellow supremacists as they questioned the validity of the tests - something scientists, for very different reasons, have also been doing.

Genetic labs, including big players like AncestryDNA, Ancestry.com and 23andMe, use preexisting datasets and reference populations that they have recruited to compare a customer's genetic makeup with genetic material from thousands of individuals and genetic variations.

But there are variables that can affect the result, such as comparing results against different datasets, while today's geopolitical borders are relatively new in terms of genetic history, which can affect which modern country a consumer's ancestors are said to have hailed from.

'There is a mainstream critical literature on genetic ancestry tests — geneticists and anthropologists and sociologists who have said precisely those things: that these tests give an illusion of certainty, but once you know how the sausage is made, you should be much more cautious about these results,' said Panofsky.