The former leader of UKIP in Wales has said he would leave the party if anti-Islam campaigner Anne Marie Waters won the leadership election.
MEP Nathan Gill said he "could not stay in a party that suddenly represented all the things that for 12 years I said it didn't represent".
Ms Waters, who founded the Sharia Watch pressure group, is one of 11 candidates in the race.
Her bid has split the party, with many angry she has been allowed to run.
Former Labour activist Ms Waters believes her anti-Islam message, including a proposed ban on burkas, the closure of sharia councils and a temporary freeze on all immigration, will appeal to many voters.