Jim Dowson, originally from Airdrie in North Lanarkshire, allegedly used advertising cash from the social media groups as well as membership fees to fund militant Christian groups in Kosovo who are preparing for “a war against Islam”.
Mr Downson, who denies the claims, was once a close ally of BNP leader Nick Griffin and a co-founder of the Britain First movement which was recently banned from Facebook.
The BBC investigation found he was the front for Knights Templar International (KTI), a Christian militant group based in the UK.
The lowest price for KTI membership is £65, which means the group could have earned hundreds of thousands of pounds in fees if claims over its memebership size are correct.
In an interview with a far-right American talk show, Mr Dowson claimed he had recently delivered “a huge consignment of bullet-proof vests and tactical equipment” to militants based in Kosovo, the former Serbian province which declared independence in 1999.
The BBC also found he had appeared in a video urging people to donate money for the purchase of equipment, saying “they need practical things like night vision goggles, tactical vests, ration packs. They need all of these things to keep an eye on this because this will kick off at any moment.”
Responding to the BBC’s claims, Mr Dowson said it was a “ludicrous assumption” to suggest that he was “stirring up tensions” in the area, adding it was important for people in the region to be given “protective vests”.
He said he “rejects violence”.
Last year Mr Dowson, who first made headlines as a militant anti-abortion campaigner, was banned from entering Hungary after being deemed a threat to national security.
A Hungarian cabinet office spokesman told the Daily Record: “James Dowson is an unwanted individual in Hungary who has been banned from the country by the immigration and asylum office.
“The authority also issued a prohibition of entry and residence order against him.
Immigration measures have been conducted on the recommendation of the counter-terrorism centre.”