Norma Woodward, standing in Carmarthen East and Dinefwr, said she had been intimidated, harassed and libelled by the UKIP Wales committee.
It said it was "extremely concerned" by Ms Woodward's comments, and had not been aware of her concerns.
UKIP Wales tried to remove her as a candidate in March over management of a party bank account, but was overruled.
The party's UK headquarters said the Wales committee did not have the power to remove candidates, and Ms Woodward would be remaining in the position.
Ms Woodward has told BBC Wales that the allegations made against her are libellous, and that she has been badly treated by UKIP Wales.
"Right from the beginning I've had a tremendous lot of intimidation and harassment, libel and slander and sexual discrimination against me as a female," she said.
"And it has made it extremely difficult.
"The campaigning itself is straightforward, the work is easy.
"It's been the bullying that's been very hard to cope with so I would like the opportunity to clear my name because I haven't committed any of these things I've been accused of in the local press and on internet and Facebook and Twitter.
"UKIP (centrally) as a party have been extremely supportive, in particular the party leader (Nigel Farage) and the chairman (Steve Crowther) have been very very supportive."
A spokesman for UKIP Wales said: "The UKIP Wales Committee is extremely concerned by these comments, which have only now been brought to our attention.
"Had these concerns been raised with the committee previously we would have investigated them immediately.
"In the meantime we will continue to talk about the issues that matter most to the Welsh people which establishment politicians continue to ignore."
A UKIP general election candidate has told BBC Wales she is planning legal action against her own party.