In the campaign, which launched at Christmas, Brigstocke plays two characters called Dan and Dan’s Data Self – the second being the personification of Dan, as he is seen by financial providers.
According to freelance video editor Haythorn, the concept bears more than a passing resemblance to videos he has been posting on YouTube for more than decade featuring two versions of himself in conversation.
A spokeswoman for the agency issued a strong rebuttal of the claim: "BBH only became informed of Mr Haythorn’s films when he approached us during the final development of the campaign. Neither BBH nor Experian were aware of Dan Haythorn's works previously and therefore any similarity between the Experian campaign and his work is purely coincidental.
"The use of doppelgangers in films, videos and other forms of art is commonplace and this was the inspiration for the Data Self campaign."
Haythorn's videos include acoustic guitar ditty The Daily Mail Song, which has racked up more than two million views.
Haythorn said he caught wind of the campaign before it had begun from a casting call, and contacted BBH to request they change the name of the character to "anything but Dan".
He told Campaign he would have been willing to believe the similarity was coincidental if it "wasn't so blatant". He added: "The names, the doppelgänger effect, the decision to cast Brigstocke whose look and tone and style of delivery so closely matches mine."
The agency has offered Haythorn what he said was a "derisory" amount to settle the matter, with conditions attached he did not agree to. He has taken legal advice from specialist IP lawyers, and said he believed he was in a strong position to bring a claim against BBH.
In the meantime, Haythorn’s latest video mocks Experian and the agency by featuring Dan & Dan discussing credit checking services, while one of two reads a copy of Hegarty on Creativity: There are No Rules, the book by BBH founder John Hegarty.
"It’s a wink to my fans – many of whom have been in contact to ask what I thought of the ads – and hopefully signals to BBH that I’m not going away," Haythorn said. "I hope BBH approve of Dan’s choice of reading matter too."