Ali Campbell believed his brothers' band was booked for Raggamuffin by the festival's Australian promoter Andrew McManus because his version of the group turned it down.
"It is unbelievable McManus is putting on the other UB40 so close to our tour," Campbell told the Herald on Sunday this week from Phoenix, Arizona.
"I think he feels a bit betrayed we decided not to do Raggamuffin after headlining it four or five times in the past.
"But in recent times there has been too many hip-hop and rap acts on the bill and we felt the festival was losing credibility with reggae fans. Last year Ice Cube went down like a horse-s*** sandwich, as Lauryn Hill did the previous year."
Ali Campbell's band features original UB40 members Terence "Astro" Wilson and Mickey Virtue. His brothers' version also contains originals - Jimmy Brown (drums), Earl Falconer (bass), Norman Hassan (percussion) and Brian Travers (saxophone and keyboards).
"I am the original voice of UB40 and everyone knows that," Campbell said.
"When people go to see the other lot it would be like going to a Rolling Stones concert and watching Mick Jagger's unknown brother Chris fronting the band. Everyone would be wondering who the hell he is.
"My brothers will find it very difficult in front of what is basically my crowd at Raggamuffin."
Raggamuffin spokesman Brotha D said the other UB40 was booked because Ali Campbell's band had already announced their own summer tour of New Zealand.
"The fans kept asking us to get UB40 on the bill and as Ali's brothers were playing in Australia around the same time it made sense for us to get them on board.
"We are not here to play politics and the beef between the two bands has nothing to do with us.
"The UB40 playing Raggamuffin are not imposters.
"They have several original members and everyone is looking forward to hearing them do the classic songs we grew up with."
A spokeswoman for Raggamuffin added that Campbell's version of the band "was never invited" to play at the festival.
"Raggamuffin is looking forward to presenting the original UB40, featuring five of the six founder members," the spokeswoman said.
"These are Robin Campbell (vocals and guitar), Jimmy Brown (drums), Earl Falconer (bass and vocals), Norman Hassan (percussion and vocals) and Brian Travers (saxophone). UB40 also features Martin Meredith and Laurence Parry, long time horn section with UB40 for over 20 years, Tony Mullings on keyboards, and Robin's brother Duncan Campbell, vocalist for eight years with UB40."
The battle over the name "UB40" is set to be played out in Britain's High Court. A hearing date is not yet confirmed.