The allegation comes at a time when Khatta Singh has filed a plea to depose against Gurmeet Ram Rahim in the murders of journalist Ram Chander Chhatrapati and former Dera manager Ranjit Singh.
Suminder Kaur, who claimed to be Khatta Singh's niece, alleged that she was being coerced by him to give false testimony against the Sirsa-based Dera chief.
"Khatta Singh has been conspiring to defame the Dera. He tried to involve me but when I didn't listen to him, I was threatened and assaulted. He also attempted to have me kidnapped," Ms Kaur claimed at a press conference.
Gurmeet Ram Rahim Singh was found guilty of rape in August this year, following an anonymous written complaint in April, 2002, that he had sexually exploited two female followers. He is serving 20 years in jail; 10 years each for the two rapes.
The trial in the two murder cases against him are in the final stages.
A Sirsa-based journalist, Ram Chander Chhatrapati was shot at in October, 2002, after he exposed alleged nefarious activities inside the Dera. He died subsequently.
The second murder relates to former Dera manager Ranjit Singh who was shot dead in 2002. He was murdered for his suspected role in the circulation of the anonymous letter, which had made the sexual exploitation allegations, according to the prosecution.